Add more interrupts handled for booke.

e500mc, e5500, and e6500 all use the normal FPU, with the same behavior as AIM
hardware. e6500 also supports Altivec, so, although we don't yet have e6500
hardware to test on, add these IVORs as well. Theoretically, since it boots the
same as a e5500, it should work, single-threaded, single-core, with full altivec
support as of this commit.

With this commit, and some other patches to be committed shortly FreeBSD now
boots on the P5020, single-core, all the way to user space, and should boot just
fine on e500mc.

Relnotes: Yes (e500mc, e5500 support)
Sponsored by: Alex Perez/Inertial Computing