[PATCH][arm] build fix for gcc-6 -Werror=shift-negative-value

[Nicholas Clifton]

Hi Szabolcs,

>   Szabolcs Nagy<szabolcs.nagy@arm.com>
>
> 	* opcodes/arm-dis.c (print_insn_coprocessor): Avoid negative shift.

Approved and applied.

Cheers
   Nick