[PATCH] RISC-V: Fix assembler for c.addi, rd can be x0

[Nick Clifton]

Hi Palmer,

> 2017-03-14  Kito Cheng  <kito.cheng@gmail.com>
> 
> 	* riscv-opc.c (riscv_opcodes) <c.addi>: Use match_opcode.

Approved - please apply.

Cheers
  Nick