aarch64: Align lrcpc3 FEAT_STRING with /proc/cpuinfo 'Features' entry

aarch64: Align lrcpc3 FEAT_STRING with /proc/cpuinfo 'Features' entry

Due to the Linux kernel exposing the lrcpc3 architectural feature as
"lrcpc3", this patch corrects the relevant FEATURE_STRING entry in the
"rcpc3" AARCH64_OPT_FMV_EXTENSION macro, such that the feature can be
correctly detected when doing native compilation on rcpc3-enabled
targets.

gcc/ChangeLog:

	* config/aarch64/aarch64-option-extensions.def (rcpc3):
	Fix FEATURE_STRING field to "lrcpc3".

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/cpunative/info_24: New.
	* gcc.target/aarch64/cpunative/native_cpu_24.c: Likewise.