Revert r216805 "[MachineCombiner][AArch64] Use the correct register class for MADD, SUB, and OR."

I think this broke the build bot. Reverting it for now until I have time to take a closer look.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216813 91177308-0d34-0410-b5e6-96231b3b80d8