[mips][microMIPS] Fix opcodes of MFHC1 and MTHC1 instructions.

Differential Revision: http://reviews.llvm.org/D6169


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222355 91177308-0d34-0410-b5e6-96231b3b80d8