s390: Add brasl edge test cases from ESA to z/Architecture

s390: Add brasl edge test cases from ESA to z/Architecture

The ESA opcode test cases for IBM z900 contain a few edge cases. They
exercise the brasl mnemonic with its largest allowed negative and
positive offsets. Linux on zSeries in ESA mode executes in 31-bit
addressing mode. Therefore the ESA test cases are assembled with -m31.
In 31-bit addressing mode the address computation using those large
offsets wraps, which is correctly reflected in the disassembly.

Linux on Z in z/Architecture mode executes in 64-bit addressing mode.
Therefore the z/Architecture (zarch) test cases are assembled with -m64.
In 64-bit addressing mode the address computation using those large
offsets does not necessarily wrap.

gas/
	* testsuite/gas/s390/zarch-z900.s: Add brasl tests from ESA that
	  exercise edge cases.
	* testsuite/gas/s390/zarch-z900.d: Likewise.

Signed-off-by: Jens Remus <jremus@linux.ibm.com>
Reviewed-by: Andreas Krebbel <krebbel@linux.ibm.com>