change argument type to bfd_byte
    
    We operate on the pointer's target as a set of bytes, and this avoids doing
    arithmetic on void * which is undefined in ISO C.
    
    bfd/ChangeLog:
    
    2016-04-20  Trevor Saunders  <tbsaunde+binutils@tbsaunde.org>
    
    	* elf32-arm.c (put_thumb2_insn): Change argument type to bfd_byte *.