[mips][msa] Requires<[HasMSA]> is redundant, it is also supplied via inheritance

Tested with 'llvm-tblgen -print-records' which outputs identical records before
and after this patch.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190155 91177308-0d34-0410-b5e6-96231b3b80d8