testsuite: Revert to the original version of pr100056.c

r15-268-g9dbff9c05520 restored the original GCC 11 output for
pr100056.c, so this patch reverts the changes made to the test
in r12-7259-g25332d2325c7.  (The code parts of r12-7259 still
seem useful, as a belt-and-braces thing.)

gcc/testsuite/
	* gcc.target/aarch64/pr100056.c: Restore the original version of
	the scan-assemblers.