This patch adds support for microMIPS disassembler and disassembler make check tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190144 91177308-0d34-0410-b5e6-96231b3b80d8
[mips][msa] Made the operand register sets optional for the 3R_4R format

Their default is to be the same as the result register set.

No functional change



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190145 91177308-0d34-0410-b5e6-96231b3b80d8