i386: Some more -mavx512vl -mno-avx512bw fixes [PR99321]

i386: Some more -mavx512vl -mno-avx512bw fixes [PR99321]

2021-03-14  Uroš Bizjak  <ubizjak@gmail.com>

gcc/
	* config/i386/sse.md (*vec_extract<mode>): Merge alternative 0 with
	alternative 2 and alternative 1 with alternative 3 using
	YW register constraint.
	(*vec_extract<PEXTR_MODE12:mode>_zext): Merge alternatives
	using YW register constraint.
	(*vec_extractv16qi_zext): Ditto.
	(*vec_extractv4si): Merge alternatives 4 and 5
	using Yw register constraint.
	(*ssse3_palignr<mode>_perm): Use Yw instead of v for alternative 3.