s390: Add test case for disassembler option warn-areg-zero gas/ * testsuite/gas/s390/s390.exp: Add test cases for s390-specific assembler option "warn-areg-zero". * testsuite/gas/s390/zarch-warn-areg-zero.s: Likewise. * testsuite/gas/s390/zarch-warn-areg-zero.l: Likewise. Reviewed-by: Andreas Krebbel <krebbel@linux.ibm.com> Signed-off-by: Jens Remus <jremus@linux.ibm.com>