[mips] Use TwoOperandAliasConstraint for ArithLogicR instructions.

This enables TableGen to generate an additional two operand matcher
for our ArithLogicR class of instructions (constituted by 3 register operands).
E.g.: and $1, $2 <=> and $1, $1, $2


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204826 91177308-0d34-0410-b5e6-96231b3b80d8