aarch64: Add rcpc3 dependency on rcpc2 and rcpc

aarch64: Add rcpc3 dependency on rcpc2 and rcpc

We don't yet have a separate feature flag for FEAT_LRCPC2 (and adding
one will require extending the feature bitmask).  Instead, make the
FEAT_LRCPC2 patterns available when either armv8.4-a or +rcpc3 is
specified.  We already have a +rcpc flag, so this dependency can be
specified directly.

Also add an explicit dependance on +rcpc to the FEAT_LRCPC2 patterns, so
that they are disabled with armv8.4-a+norcpc.

The cpunative test needed updating because it used an invalid Features
list, since lrcpc3 requires both ilrcpc and lrcpc to be present.
Without this change, host_detect_local_cpu would return the architecture
string 'armv8-a+dotprod+crc+crypto+rcpc3+norcpc'.

gcc/ChangeLog:

	* config/aarch64/aarch64-option-extensions.def: Add RCPC to
	RCPC3 dependencies.
	* config/aarch64/aarch64.h (AARCH64_ISA_RCPC8_4): Add test for
	RCPC3 bit

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/cpunative/info_24: Include lrcpc and ilrcpc.