aarch64: Use type-qualified builtins for UADD[LW][2] Neon intrinsics

aarch64: Use type-qualified builtins for UADD[LW][2] Neon intrinsics

Declare unsigned type-qualified builtins and use them to implement
widening-add Neon intrinsics. This removes the need for many casts in
arm_neon.h.

gcc/ChangeLog:

2021-11-09  Jonathan Wright  <jonathan.wright@arm.com>

	* config/aarch64/aarch64-simd-builtins.def: Use BINOPU type
	qualifiers in generator macros for uadd[lw][2] builtins.
	* config/aarch64/arm_neon.h (vaddl_s8): Remove unnecessary
	cast.
	(vaddl_s16): Likewise.
	(vaddl_s32): Likewise.
	(vaddl_u8): Use type-qualified builtin and remove casts.
	(vaddl_u16): Likewise.
	(vaddl_u32): Likewise.
	(vaddl_high_s8): Remove unnecessary cast.
	(vaddl_high_s16): Likewise.
	(vaddl_high_s32): Likewise.
	(vaddl_high_u8): Use type-qualified builtin and remove casts.
	(vaddl_high_u16): Likewise.
	(vaddl_high_u32): Likewise.
	(vaddw_s8): Remove unnecessary cast.
	(vaddw_s16): Likewise.
	(vaddw_s32): Likewise.
	(vaddw_u8): Use type-qualified builtin and remove casts.
	(vaddw_u16): Likewise.
	(vaddw_u32): Likewise.
	(vaddw_high_s8): Remove unnecessary cast.
	(vaddw_high_s16): Likewise.
	(vaddw_high_s32): Likewise.
	(vaddw_high_u8): Use type-qualified builtin and remove casts.
	(vaddw_high_u16): Likewise.
	(vaddw_high_u32): Likewise.