The SCHEDULER_IDENT for this CPU was incorrectly
set to cortexa55, which is incorrect. This can cause
sub-optimal asm to be generated.

Ok for trunk?

gcc/ChangeLog:
	PR target/114272
	* config/aarch64/aarch64-cores.def (AARCH64_CORE):
	Change SCHEDULER_IDENT from cortexa55 to cortexa53
	for Cortex-A520.