[ARM] Hide existing float16 intrinsics unless we have a scalar __fp16 type

[ARM] Hide existing float16 intrinsics unless we have a scalar __fp16 type

gcc/:

	* config/arm/arm-builtins.c (arm_init_simd_builtin_types): Move
	initialization of HFmode scalar type (float16_t) to...
	(arm_init_fp16_builtins): ... Here. Combine with __fp16 initialization
	code.

	(arm_init_builtins): Call arm_init_fp16_builtins earlier and always.

	* config/arm/arm_neon.h (vcvt_f16_f32, vcvt_f32_f16): Condition on
	having an -mfp16-format.

gcc/testsuite/:

	* lib/target-supports.exp
	(check_effective_target_arm_neon_fp16_ok_nocache): Add flag variants
	with -mfp16-format=ieee.

From-SVN: r227033