[AArch64] Fix -Wimplicit-fallthrough warnings. NFCI.
[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: 0ff597fd157e6f4fc38580e8d64ab130330d2411@307484 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm