rs6000.c (print_operand, 'z'): Remove historical hack to mark symbols as used.

2013-06-09  David Edelsohn  <dje.gcc@gmail.com>
            Jan Hubicka  <jh@suse.cz>

        * config/rs6000/rs6000.c (print_operand, 'z'): Remove historical
        hack to mark symbols as used.

Co-Authored-By: Jan Hubicka <jh@suse.cz>

From-SVN: r199865