cache-coherent shared memory on zynq

[Jamey Hicks]

I checked in some changes so that Connectal applications can use the ACP port and perform reads and writes that are snooped by the processor's L1 caches.

Just define USE_ACP when building the application, and use portalAllocCached to allocate the memory regions.

In your Makefile:

    CONNECTALFLAGS += -D USE_ACP

The first memory master from mkConnectalTop will be connected to the ACP.

Although it is possible to specify on a per-request basis whether it should be snooped or not, I did not expose that functionality. It makes more sense to me to steer those requests to one of the ports that does not go through the CPU cache in that case.

I will change the default for portalAlloc to cached, even for the non-snooped ports, if it improves performance in those cases.

-Jamey