[mips] Added missing daddu test to the valid instruction tests.

Summary: Depends on D3673

Reviewers: vmedic

Reviewed By: vmedic

Differential Revision: http://reviews.llvm.org/D3674

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208398 91177308-0d34-0410-b5e6-96231b3b80d8