[mips][msa] copyPhysReg() should not set RegState::Define on result of CTCMSA.

Summary:
The machine verifier reports 'Explicit operand marked as def' when it is
manually specified even though it agrees with the operand info.

Reviewers: sdardis

Subscribers: dsanders, sdardis, llvm-commits

Differential Revision: http://reviews.llvm.org/D21065

llvm-svn: 272646