i386: Fix the pmovzx SSE4.1 define_insn_and_split patterns [PR98670]

i386: Fix the pmovzx SSE4.1 define_insn_and_split patterns [PR98670]

I've made two mistakes in the *sse4_1_zero_extend* define_insn_and_split
patterns.  One is that when it uses vector_operand, it should use Bm rather
than m constraint, and the other one is that because it is a post-reload
splitter it needs isa attribute to select which alternatives are valid for
which ISAs.  Sorry for messing this up.

2021-01-14  Jakub Jelinek  <jakub@redhat.com>

	PR target/98670
	* config/i386/sse.md (*sse4_1_zero_extendv8qiv8hi2_3,
	*sse4_1_zero_extendv4hiv4si2_3, *sse4_1_zero_extendv2siv2di2_3):
	Use Bm instead of m for non-avx.  Add isa attribute.

	* gcc.target/i386/pr98670.c: New test.