[mips][msa] Direct Object Emission for 2R instructions.

This patch adds Direct Object Emission support for 2R instructions: nloc.{b,h,w}, nlzc.{b,h,w}, pcnt.{b,w,d}.  


Patch by Matheus Almeida


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191685 91177308-0d34-0410-b5e6-96231b3b80d8