AArch64: stop trying to use 32-bit MOVZs when expanding patchpoints.

Of course the assembly was right but because the opcode was MOVZWi it was
encoded as "movz w16, #65535, lsl #32" which is an unallocated encoding and
would go horribly wrong on a CPU.

No idea how this bug survived this long. It seems nobody is using that aspect
of patchpoints.

llvm-svn: 272831