addi/daddi are deprecated by MIPS for years, and MIPS r6 remove
them.

They should be replace with addiu:
   ADDIU performs the same arithmetic operation but
   does not trap on overflow.
Reviewed-by: Shiyou Yin <yinshiyou-hf@loongson.cn>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>