Probably something to do with the am335x-pru0-fw and am335x-pru1-fw. Did you generate these yourself and are they derived from V4 of the PRU Software Support Package? Here is what the log should look like
[ 17.730877] pruss-rproc 4a300000.pruss: 8 PRU interrupts parsed
[ 17.730963] pruss-rproc 4a300000.pruss: memory dram0: pa 0x4a300000 size 0x2000 va e0cfc000
[ 17.730992] pruss-rproc 4a300000.pruss: memory dram1: pa 0x4a302000 size 0x2000 va e0d00000
[ 17.731016] pruss-rproc 4a300000.pruss: memory shrdram2: pa 0x4a310000 size 0x3000 va e0d04000
[ 17.731061] pruss-rproc 4a300000.pruss: memory intc: pa 0x4a320000 size 0x2000 va e0d08000
[ 17.731085] pruss-rproc 4a300000.pruss: memory cfg: pa 0x4a326000 size 0x2000 va e0d0c000
[ 17.739291] pruss-rproc 4a300000.pruss: creating platform devices for PRU cores
[ 17.838694] pru-rproc 4a334000.pru0: memory iram: pa 0x4a334000 size 0x2000 va e0d10000
[ 17.838750] pru-rproc 4a334000.pru0: memory control: pa 0x4a322000 size 0x400 va e0876000
[ 17.838807] pru-rproc 4a334000.pru0: memory debug: pa 0x4a322400 size 0x100 va e09fe400
[ 17.839055] remoteproc1: 4a334000.pru0 is available
[ 17.889681] remoteproc1: Note: remoteproc is still under development and considered experimental.
[ 17.976790] remoteproc1: THE BINARY FORMAT IS NOT YET FINALIZED, and backward compatibility isn't yet guaranteed.
[ 18.110269] remoteproc1: registered virtio0 (type 7)
[ 18.117784] pru-rproc 4a334000.pru0: PRU rproc node /ocp/pruss@4a300000/pru@4a334000 probed successfully
[ 18.179627] pru-rproc 4a338000.pru1: memory iram: pa 0x4a338000 size 0x2000 va e0d40000
[ 18.179703] pru-rproc 4a338000.pru1: memory control: pa 0x4a324000 size 0x400 va e0cfa000
[ 18.179731] pru-rproc 4a338000.pru1: memory debug: pa 0x4a324400 size 0x100 va e0d44400
[ 18.179991] remoteproc2: 4a338000.pru1 is available
[ 18.238845] remoteproc2: Note: remoteproc is still under development and considered experimental.
[ 18.379910] remoteproc2: THE BINARY FORMAT IS NOT YET FINALIZED, and backward compatibility isn't yet guaranteed.
[ 18.632315] remoteproc2: registered virtio1 (type 7)
[ 18.650550] pru-rproc 4a338000.pru1: PRU rproc node /ocp/pruss@4a300000/pru@4a338000 probed successfully
[ 20.207007] remoteproc1: powering up 4a334000.pru0
[ 20.494385] remoteproc1: Booting fw image am335x-pru0-fw, size 78652
[ 20.500992] pru-rproc 4a334000.pru0: version 0 event_chnl_map_size 1 event_chnl_map 0000039c
[ 20.501012] pru-rproc 4a334000.pru0: sysevt-to-ch[60] -> 0
[ 20.501027] pru-rproc 4a334000.pru0: chnl-to-host[0] -> 0
[ 20.501040] pru-rproc 4a334000.pru0: skip intr mapping for chnl 1
[ 20.501052] pru-rproc 4a334000.pru0: skip intr mapping for chnl 2
[ 20.501064] pru-rproc 4a334000.pru0: skip intr mapping for chnl 3
[ 20.501076] pru-rproc 4a334000.pru0: skip intr mapping for chnl 4
[ 20.501088] pru-rproc 4a334000.pru0: skip intr mapping for chnl 5
[ 20.501100] pru-rproc 4a334000.pru0: skip intr mapping for chnl 6
[ 20.501112] pru-rproc 4a334000.pru0: skip intr mapping for chnl 7
[ 20.501124] pru-rproc 4a334000.pru0: skip intr mapping for chnl 8
[ 20.501136] pru-rproc 4a334000.pru0: skip intr mapping for chnl 9
[ 20.501153] pruss-rproc 4a300000.pruss: SYSEV60 -> CH0 (CMR15 0x00000000)
[ 20.501168] pruss-rproc 4a300000.pruss: CH0 -> HOST0 (HMR0 0x00000000)
[ 20.501183] pruss-rproc 4a300000.pruss: configured system_events = 0x1000000000000000 intr_channels = 0x00000001 host_intr = 0x00000001
[ 20.736524] remoteproc1: starting PRU0: entry-point = 0x0
[ 20.767050] remoteproc1: remote processor 4a334000.pru0 is now up
[ 20.873912] remoteproc1: mbox msg: 0x0
[ 20.873976] virtio_rpmsg_bus virtio0: creating channel rpmsg-client-sample addr 0x1e
[ 20.914002] remoteproc1: kicking vqid 0 on PRU0
[ 20.914078] virtio_rpmsg_bus virtio0: rpmsg host is online
[ 20.989597] remoteproc1: kicking vqid 0 on PRU0
[ 21.071282] remoteproc2: powering up 4a338000.pru1
[ 21.247641] remoteproc2: Booting fw image am335x-pru1-fw, size 78644
[ 21.335040] pru-rproc 4a338000.pru1: version 0 event_chnl_map_size 1 event_chnl_map 00000394
[ 21.335079] pru-rproc 4a338000.pru1: sysevt-to-ch[59] -> 1
[ 21.335094] pru-rproc 4a338000.pru1: skip intr mapping for chnl 0
[ 21.335108] pru-rproc 4a338000.pru1: chnl-to-host[1] -> 1
[ 21.335120] pru-rproc 4a338000.pru1: skip intr mapping for chnl 2
[ 21.335132] pru-rproc 4a338000.pru1: skip intr mapping for chnl 3
[ 21.335144] pru-rproc 4a338000.pru1: skip intr mapping for chnl 4
[ 21.335156] pru-rproc 4a338000.pru1: skip intr mapping for chnl 5
[ 21.335168] pru-rproc 4a338000.pru1: skip intr mapping for chnl 6
[ 21.335180] pru-rproc 4a338000.pru1: skip intr mapping for chnl 7
[ 21.335192] pru-rproc 4a338000.pru1: skip intr mapping for chnl 8
[ 21.335204] pru-rproc 4a338000.pru1: skip intr mapping for chnl 9
[ 21.335222] pruss-rproc 4a300000.pruss: SYSEV59 -> CH1 (CMR14 0x01000000)
[ 21.335236] pruss-rproc 4a300000.pruss: SYSEV60 -> CH0 (CMR15 0x00000000)
[ 21.335251] pruss-rproc 4a300000.pruss: CH0 -> HOST0 (HMR0 0x00000000)
[ 21.335265] pruss-rproc 4a300000.pruss: CH1 -> HOST1 (HMR0 0x00000100)
[ 21.335281] pruss-rproc 4a300000.pruss: configured system_events = 0x1800000000000000 intr_channels = 0x00000003 host_intr = 0x00000003
[ 21.508227] remoteproc2: starting PRU1: entry-point = 0x0
[ 21.508264] remoteproc2: remote processor 4a338000.pru1 is now up
[ 21.615803] remoteproc2: mbox msg: 0x0
[ 21.615861] virtio_rpmsg_bus virtio1: creating channel rpmsg-pru addr 0x1f
[ 21.627159] remoteproc2: kicking vqid 0 on PRU1
[ 21.627220] virtio_rpmsg_bus virtio1: rpmsg host is online
[ 21.640975] remoteproc2: kicking vqid 0 on PRU1
[ 22.905600] rpmsg_pru rpmsg1: new rpmsg_pru device: /dev/rpmsg_pru31