[mips] Add instruction aliases for ds(r|l)l.

[mips] Add instruction aliases for ds(r|l)l.

Add the instruction aliases for ds(r|l)l for the two operand alias
of ds(r|l)lv and the aliases ds(r|l)l with the three register operands.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306405 91177308-0d34-0410-b5e6-96231b3b80d8