IBM Z: Fix load-and-test peephole2 condition

IBM Z: Fix load-and-test peephole2 condition

For a peephole2 condition variable insn points to the first matched
insn.  In order to refer to the second matched insn use
peep2_next_insn(1) instead.

gcc/ChangeLog:

	* config/s390/s390.md (define_peephole2): Variable insn points
	to the first matched insn.  Use peep2_next_insn(1) to refer to
	the second matched insn.

gcc/testsuite/ChangeLog:

	* gcc.target/s390/20211119.c: New test.

(cherry picked from commit f47870e6a272dfe740a38422030c6c68e0fc7ff8)