Support commutative alternative for AVX512 vpcmpeq{b,w,d,q}

Support commutative alternative for AVX512 vpcmpeq{b,w,d,q}

gcc/ChangeLog:

	* config/i386/sse.md
	(*<avx512>_eq<mode>3<mask_scalar_merge_name>_1): Extend to
	UNSPEC_PCMP_UNSIGNED.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr103774.c: New test.
	* gcc.target/i386/avx512bw-vpcmpequb-1.c: Adjust scan assembler
	from vpcmpub to (?:vpcmpub|vpcmpeqb).
	* gcc.target/i386/avx512bw-vpcmpequw-1.c: Ditto.
	* gcc.target/i386/avx512bw-vpcmpub-1.c: Ditto.
	* gcc.target/i386/avx512bw-vpcmpuw-1.c: Ditto.
	* gcc.target/i386/avx512f-vpcmpequd-1.c: Ditto.
	* gcc.target/i386/avx512f-vpcmpequq-1.c: Ditto.
	* gcc.target/i386/avx512f-vpcmpud-1.c: Ditto.
	* gcc.target/i386/avx512vl-vpcmpequd-1.c: Ditto.
	* gcc.target/i386/avx512vl-vpcmpequq-1.c: Ditto.
	* gcc.target/i386/avx512vl-vpcmpuq-1.c: Ditto.