[mips][msa] Direct Object Emission for I8 instructions.

This patch adds Direct Object Emission support for I8 instructions: andi.b, bmnzi.b, bmzi.b, bseli.b, nori.b, ori.b, shf.{b,h,w} and xori.b.


Patch by Matheus Almeida


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191688 91177308-0d34-0410-b5e6-96231b3b80d8