[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

llvm-svn: 191688