[mips] Unified the MipsMemSimm9GPRAsmOperand and MipsMemSimm9AsmOperand operands, NFC.
Summary:
These operands had the same purpose, however the MipsMemSimm9GPRAsmOperand
operand was only for micromips32r6 and the MipsMemSimm9AsmOperand did not
have a ParserMatchClass.
Patch by Scott Egerton
Reviewers: vkalintiris, dsanders
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D12730
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247573
91177308-0d34-0410-b5e6-
96231b3b80d8