x86: harmonize __builtin_ia32_psadbw*() types

x86: harmonize __builtin_ia32_psadbw*() types

The 64-bit, 128-bit, and 512-bit variants have V<n>DI return type, in
line with instruction behavior. Make the 256-bit builtin match, thus
also making it match the insn it expands to (using VI8_AVX2_AVX512BW).

gcc/

	* config/i386/i386-builtin.def (__builtin_ia32_psadbw256):
	Change type.
	* config/i386/i386-builtin-types.def: New function type
	(V4DI, V32QI, V32QI).
	* config/i386/i386-expand.cc (ix86_expand_args_builtin): Handle
	V4DI_FTYPE_V32QI_V32QI.