aarch64: Relax flags for floating-point builtins to FP where appropriate

aarch64: Relax flags for floating-point builtins to FP where appropriate

This patch relaxes various floating-point builtins to use the FP flags to signify they
made use the FPCR or raise exceptions.

gcc/ChangeLog:

	* config/aarch64/aarch64-simd-builtins.def (fcmla_lane0, fcmla_lane90,
	fcmla_lane180, fcmla_lane270, fcmlaq_lane0, fcmlaq_lane90, fcmlaq_lane180,
	fcmlaq_lane270, scvtf, ucvtf, fcvtzs, fcvtzu, scvtfsi, scvtfdi, ucvtfsi,
	ucvtfdi, fcvtzshf, fcvtzuhf, fmlal_lane_low, fmlsl_lane_low,
	fmlal_laneq_low, fmlsl_laneq_low, fmlalq_lane_low, fmlslq_lane_low,
	fmlalq_laneq_low, fmlslq_laneq_low, fmlal_lane_high, fmlsl_lane_high,
	fmlal_laneq_high, fmlsl_laneq_high, fmlalq_lane_high, fmlslq_lane_high,
	fmlalq_laneq_high, fmlslq_laneq_high): Use FP flags.