[AArch64] Fix -Wimplicit-fallthrough warnings. NFCI.

Add breaks - doesn't affect results as both GPR/FPU both check for 32/64 bit sizes. So will still default to GenericOps in the same way.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307484 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed