Fix ARM paired GPR COPY lowering

ARM paired GPR COPY was being lowered to two MOVr without CC. This
patch puts the CC back.

My test is a reduction of the case where I encountered the issue,
64-bit atomics use paired GPRs.

The issue only occurs with selectionDAG, FastISel doesn't encounter it
so I didn't bother calling it.

llvm-svn: 186226