i386: Fix up *avx_vperm_broadcast_v4df [PR93430]

Apparently my recent patch which moved the *avx_vperm_broadcast* and
*vpermil* patterns before vpermpd broke the following testcase, the
define_insn_and_split matched always but the splitter condition only split
it if not -mavx2 for V4DFmode, basically relying on the vpermpd pattern to
come first.

The following patch fixes it by moving that part of SPLIT-CONDITION into
CONDITION, so that when it is not met, we just don't match the pattern
and thus match the later vpermpd pattern in that case.
Except, for { 0, 0, 0, 0 } permutation, there is actually no reason to do
that, vbroadcastsd from memory seems to be slightly cheaper than vpermpd $0.

2020-01-26  Jakub Jelinek  <jakub@redhat.com>

	PR target/93430
	* config/i386/sse.md (*avx_vperm_broadcast_<mode>): Disallow for
	TARGET_AVX2 and V4DFmode not in the split condition, but in the
	pattern condition, though allow { 0, 0, 0, 0 } broadcast always.

	* gcc.dg/pr93430.c: New test.
	* gcc.target/i386/avx2-pr93430.c: New test.