aarch64: Fix assert checking alias feature bits

Adjust the assert in aarch64_get_extension_string_for_isa_flags to check
that the isa_flags parameter has no alias bits set.  This is the check I
intended to use when adding the assert in r15-7196-gb53781ce1e49fc, but
I accidentally checked the global aarch64_isa_flags value instead.

Additionally, remove the cpuinfo feature string entries for alias
features, so that the bits are left unset during host_detect_local_cpu.
Setting the bits would trigger the fixed assert, but was otherwise
harmless because aarch64_get_extension_string_for_isa_flags would ignore
the value of those bits.

gcc/ChangeLog:

	* common/config/aarch64/aarch64-common.cc
	(aarch64_get_extension_string_for_isa_flags): Check isa_flags.
	* config/aarch64/aarch64-option-extensions.def
	(CRYPTO, SVE2_AES, SVE2_BITPERM, SVE2_SHA3, SVE2_SM4): Remove
	cpuinfo feature string.