aarch64: Make AARCH64_FL_CRYPTO always unset

aarch64: Make AARCH64_FL_CRYPTO always unset

This feature flag bit only exists to support the +crypto alias.  Outside
of option processing this bit needs to be set or unset consistently.
This patch goes with the latter option.

gcc/ChangeLog:

	* common/config/aarch64/aarch64-common.cc: Assert that CRYPTO
	bit is not set.
	* config/aarch64/aarch64-feature-deps.h
	(info<FEAT>.explicit_on): Unset CRYPTO bit.
	(cpu_##CORE_IDENT): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/crypto-alias-1.c: New test.