Book-E pmap_mapdev_attr() improvements

• Check TLB1 in all mapdev cases, in case the memattr matches an existing mapping (doesn't need to be MAP_DEFAULT).
• Fix mapping where the starting address is not a multiple of the widest size base. For instance, it will now properly map 0xffffef000, size 0x11000 using 2 TLB entries, basing it at 0x**f000, instead of 0x*00000.

MFC after: 2 weeks