[PATCH] aarch64: Implement vmlsl[_high]* intrinsics using builtins

[PATCH] aarch64: Implement vmlsl[_high]* intrinsics using builtins

This patch reimplements some more intrinsics using RTL builtins in the
straightforward way.
Thankfully most of the RTL infrastructure is already in place for it.

gcc/
	* config/aarch64/aarch64-simd.md (*aarch64_<su>mlsl_hi<mode>):
	Rename to...
	(aarch64_<su>mlsl_hi<mode>): ... This.
	(aarch64_<su>mlsl_hi<mode>): Define.
	(*aarch64_<su>mlsl<mode): Rename to...
	(aarch64_<su>mlsl<mode): ... This.
	* config/aarch64/aarch64-simd-builtins.def (smlsl, umlsl,
	smlsl_hi, umlsl_hi): Define builtins.
	* config/aarch64/arm_neon.h (vmlsl_high_s8, vmlsl_high_s16,
	vmlsl_high_s32, vmlsl_high_u8, vmlsl_high_u16, vmlsl_high_u32,
	vmlsl_s8, vmlsl_s16, vmlsl_s32, vmlsl_u8,
	vmlsl_u16, vmlsl_u32): Reimplement with builtins.