Extend pmap to support e500mc and e5500.

As part of this, clean up tlb1_init(), since bootinfo is always NULL here just
eliminate the loop altogether.

Also, fix a bug in mmu_booke_mapdev_attr() where it's possible to map a larger
immediately following a smaller page, causing the mappings to overlap. Instead,
break up the new mapping into smaller chunks. The downside to this is that it
uses more precious TLB1 entries, which, on smaller chips (e500v2) it could cause
problems with TLB1 being out of space (e500v2 only has 16 TLB1 entries).

Obtained from: Semihalf (partial)
Sponsored by: Alex Perez/Inertial Computing