testsuite: arm: Use effective-target for crc_hf_1.c test

Update test cases to use -mcpu=unset/-march=unset feature introduced in
r15-3606-g7d6c6a0d15c.

gcc/testsuite/ChangeLog:

	* gcc.target/arm/acle/crc_hf_1.c: Use effective-target
	arm_arch_v8a_crc_hard.
	* lib/target-supports.exp: Define effective-target
	arm_arch_v8a_crc_hard.

Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>