S/390: Improve result verification in test case vec-genmask-1.c.

S/390: Improve result verification in test case vec-genmask-1.c.

THe attached patch improves checking of teh results of the subtests
"a" and "f".  As they share the same "vone" instruction, the duplicate
scan-assembler-times was bogus.  Moved "f" to a separate function to
fix this.  Also double check that no extra "vgmf" instructions are
used.

gcc/testsuite/ChangeLog:

2016-08-23  Dominik Vogt  <vogt@linux.vnet.ibm.com>

	* gcc.target/s390/zvector/vec-genmask-1.c: Improve result
	verification.

From-SVN: r239686