[mips][microMIPS] Implement SUBQ[_S].PH, SUBQ_S.W, SUBQH[_R].PH, SUBQH[_R].W,...

[mips][microMIPS] Implement SUBQ[_S].PH, SUBQ_S.W, SUBQH[_R].PH, SUBQH[_R].W, SUBU[_S].PH, SUBU[_S].QB and SUBUH[_R].QB instructions
Differential Revision: http://reviews.llvm.org/D14114

llvm-svn: 253329