* dec_5100.c: sysconf, interrupt, and motherboard (drain writebuffer)
support for 5100.
* support for hardware kludge in 5100: sii DMA buffer is hardware
padded to alternate 32-bit words, not alternating 16-bit halfwords.
* 5100 has no framebuffer, console is wired to serial port 0.
With ibus support, boots as far as exec'ing init, and hangs.
as pmax/dev/findcons.c:
* Follow the same logic: look for the device the PROM is using.
* If it's a framebuffer and we don't have a driver for it, try other
* framebuffers in PROM search order.
* If no match found, warn user and fall over to serial console.
* if no serial console found, go back to PROM.
Rework tc/scc.c attach routine to give cleaner initialization semantics.
Prune out old 'braindamage' code.
jonathan