Support -mevex512 for AVX512DQ intrins

Support -mevex512 for AVX512DQ intrins

gcc/ChangeLog:

	* config/i386/i386-expand.cc (ix86_expand_sse2_mulvxdi3):
	Add TARGET_EVEX512 for 512 bit usage.
	* config/i386/i386.cc (standard_sse_constant_opcode): Ditto.
	* config/i386/sse.md (VF1_VF2_AVX512DQ): Ditto.
	(VF1_128_256VL): Ditto.
	(VF2_AVX512VL): Ditto.
	(VI8_256_512): Ditto.
	(<mask_codefor>fixuns_trunc<mode><sseintvecmodelower>2<mask_name>):
	Ditto.
	(AVX512_VEC): Ditto.
	(AVX512_VEC_2): Ditto.
	(VI4F_BRCST32x2): Ditto.
	(VI8F_BRCST64x2): Ditto.