[AArch64] Use the correct register class for ORR.

While fixing up the register classes in the machine combiner in a previous
commit I missed one.

This fixes the last one and adds a test case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221308 91177308-0d34-0410-b5e6-96231b3b80d8