Add support for Fujitsu SPARC64-VI CPUs.

Add support for Fujitsu SPARC64-VI CPUs.

UltraSPARC I/II has a 41-bit physical address space, UltraSPARC III/IV has a
43-bit physical address space.  The Fujitsu SPARC64-VI extends this to 46 bits.
Adjust the TTE masks to take this into account and adjust some locore code
that truncated physical addresses to 41 bits (fixing a potential bug for
UltraSPARC III/IV too).

While there, fix the locore code for UltraSPARC Architecture 2007 CPUs, which
may support up to 56 bits of physical address space.