[mips] Implement jr.hb and jalr.hb (Jump Register and Jump and Link Register with Hazard Barrier).

Summary: These instructions are available in ISAs >= mips32/mips64. For mips32r6/mips64r6, jr.hb has a new encoding format.

Reviewers: dsanders

Reviewed By: dsanders

Differential Revision: http://reviews.llvm.org/D4019

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210654 91177308-0d34-0410-b5e6-96231b3b80d8