353ca54019
stub for memsize_bitmap() to use the PROM bitmap for memory information.
Add a memsize function pointer to the platform structure, and make all
existing DECstation models use memsize_scan() for now.
Interestingly, from the Ultrix cpuconf.{c,h} only the 3100 and 5400 use
a memory scan to determine available memory - all other models use the
PROM bitmap...