MSCP drive geometries fixed

[rsx11m]

hey all!

you may have run into an issue recently where trying to use some types of emulated disk (specifically the RA81 in my experience) would crash the qbone- for me, this was occurring in VMS <= 4.7 and RSTS/E 10.1. well, thanks to josh, joerg, and a commit from joan, this has been fixed and an OS will now successfully boot off an emulated RA81. just update-code.sh at your earliest convenience.

thanks again guys! :)

- hush