[ARM] Fix MOVCC peephole to not use an incorrect register class

The MOVCC peephole eliminates a MOVCC by making one of its inputs a
conditional instruction, but when doing this it should be using both
inputs of the MOVCC to decide on the register class to use as
otherwise we can get an error when using -verify-machineinstrs.

Differential Revision: https://reviews.llvm.org/D111714