Use aapcs_is_vfp_call_or_return_candidate to detect float register
args.

gdb/
	PR gdb/22943:
	* aarch64-tdep.c (is_hfa_or_hva): Remove function.
	(aarch64_extract_return_value): Use
	aapcs_is_vfp_call_or_return_candidate.
	(aarch64_return_in_memory): Likewise.
	(aarch64_store_return_value): Likewise.