[AArch64] Fix optimizeCondBranch logic.

The opcode for the optimized branch does not depend on the size
of the activate bits in the AND masks, but the AND opcode itself.
Indeed, we need to use a X or W variant based on the AND variant
not based on whether the mask fits into the related variant.
Otherwise, we may end up using the W variant of the optimized branch
for 64-bit register inputs!

This fixes the last make check verifier issues for AArch64: PR27479.

llvm-svn: 267206