properties such as "M68040" and "M68K_MMU_MOTOROLA", used to conditionally
compile code. This is more in-line with now the other m68k ports do it,
and makes it much easier to find "common ground" among them.
In locore.s, use the MMU-type constants defined my <machine/cpu.h> rather
than "expanded" values.
Because HP300-model names are mapped to CPU/MMU combinations in
<machine/cpu.h>, no change to kernel configuration will be necessary.
