svn revisions r269964 and r269963 seemed to have impaired small memory
footprint systems(32M/64M) and didn't leave enough free memory to load modules
when it was setting up page tables that for sizes that are never used on
these smallish boards.

Set kmem_zmax to PAGE_SIZE on these smaller systems (< 128M) to keep this
from happening. Verified on mips32 h/w.

PR: 193465
Submitted by: delphij
Reviewed by: adrian