Support logic shift left/right for avx512 mask type.

Support logic shift left/right for avx512 mask type.

gcc/ChangeLog:

	* config/i386/constraints.md (Wb): New constraint.
	(Ww): Ditto.
	* config/i386/i386.md (*ashlhi3_1): Extend to avx512 mask
	shift.
	(*ashlqi3_1): Ditto.
	(*<insn><mode>3_1): Split to ..
	(*ashr<mode>3_1): this, ...
	(*lshr<mode>3_1): and this, also extend this pattern to avx512
	mask registers.
	(*<insn><mode>3_1): Split to ..
	(*ashr<mode>3_1): this, ...
	(*lshrqi3_1): and this, also extend this pattern to avx512
	mask registers.
	(*lshrhi3_1): And this, also extend this pattern to avx512
	mask registers.
	* config/i386/sse.md (k<code><mode>): New define_split after
	it to convert generic shift pattern to mask shift ones.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/mask-shift.c: New test.