were using a class defined for 32 bit instructions and
thus the instruction was for addiu instead of daddiu.
This was corrected by adding the instruction opcode as a
field in the base class to be filled in by the defs.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161359 91177308-0d34-0410-b5e6-96231b3b80d8
