Refine splitters related to "combine vpcmpuw + zero_extend to vpcmpuw"

Refine splitters related to "combine vpcmpuw + zero_extend to vpcmpuw"

r12-6103-g1a7ce8570997eb combines vpcmpuw + zero_extend to vpcmpuw
with the pre_reload splitter, but the splitter transforms the
zero_extend into a subreg which make reload think the upper part is
garbage, it's not correct.

The patch adjusts the zero_extend define_insn_and_split to
define_insn to keep zero_extend.

gcc/ChangeLog:

	PR target/117159
	* config/i386/sse.md
	(*<avx512>_cmp<V48H_AVX512VL:mode>3_zero_extend<SWI248x:mode>):
	Change from define_insn_and_split to define_insn.
	(*<avx512>_cmp<VI12_AVX512VL:mode>3_zero_extend<SWI248x:mode>):
	Ditto.
	(*<avx512>_ucmp<VI12_AVX512VL:mode>3_zero_extend<SWI248x:mode>):
	Ditto.
	(*<avx512>_ucmp<VI48_AVX512VL:mode>3_zero_extend<SWI248x:mode>):
	Ditto.
	(*<avx512>_cmp<V48H_AVX512VL:mode>3_zero_extend<SWI248x:mode>_2):
	Split to the zero_extend pattern.
	(*<avx512>_cmp<VI12_AVX512VL:mode>3_zero_extend<SWI248x:mode>_2):
	Ditto.
	(*<avx512>_ucmp<VI12_AVX512VL:mode>3_zero_extend<SWI248x:mode>_2):
	Ditto.
	(*<avx512>_ucmp<VI48_AVX512VL:mode>3_zero_extend<SWI248x:mode>_2):
	Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr117159.c: New test.
	* gcc.target/i386/avx512bw-pr103750-1.c: Remove xfail.
	* gcc.target/i386/avx512bw-pr103750-2.c: Remove xfail.

(cherry picked from commit 5259d3927c1c8e3a15b4b844adef59b48c241233)