Force the intregs ptr into R2 and the FPregs ptr into R3. This fixes a really

obscure problem where we were doing:

lmw     r3,0(r9)

which is undefined on PPC.  Now we do:

lmw     r3,0(r2)

by force, not relying on the GCC register allocator for luck :)

llvm-svn: 18212