[mips][msa] Add copy_{u,s}.d.

These instructions are only available on Mips64 cores
that implement the MSA ASE.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200398 91177308-0d34-0410-b5e6-96231b3b80d8
[mips][msa] CHECK-DAG-ize MSA 2r_vector_scalar.ll test.

This update is a preparation for the addition of Mips64 MSA tests.

No functional changes.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200399 91177308-0d34-0410-b5e6-96231b3b80d8