AArch64: Avoid the ICE on empty reduction definition in info_for_reduction [PR110625]

AArch64: Avoid the ICE on empty reduction definition in info_for_reduction [PR110625]

Fix the assertion failure on empty reduction define in info_for_reduction.
Even a stmt is live, it may still have empty reduction define.  Check the
reduction definition instead of live info before calling info_for_reduction.

gcc/ChangeLog:

	PR target/110625
	* config/aarch64/aarch64.cc (aarch64_force_single_cycle): check
	STMT_VINFO_REDUC_DEF to avoid failures in info_for_reduction.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/pr110625_3.c: New testcase.