[mips][mips64r6] Added mul/mulu/muh/muhu

Summary: The 'mul' line of the test is temporarily commented out because it currently matches the MIPS32 mul instead of the MIPS32r6 mul. This line will be uncommented when we disable the MIPS32 mul on MIPS32r6.

Reviewers: jkolek, zoran.jovanovic, vmedic

Reviewed By: vmedic

Differential Revision: http://reviews.llvm.org/D3668

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208576 91177308-0d34-0410-b5e6-96231b3b80d8