[mips] Added support for various EVA ASE instructions.

Summary:
Added support for the following instructions:

CACHEE, LBE, LBUE, LHE, LHUE, LWE, LLE, LWLE, LWRE, PREFE,
SBE, SHE, SWE, SCE, SWLE, SWRE, TLBINV, TLBINVF

This required adding some infrastructure for the EVA ASE.

Patch by Scott Egerton.

Reviewers: vkalintiris, dsanders

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11139

llvm-svn: 247669