testsuite: Fix up gcc.target/i386/sse4_1-stv-1.c test [PR113452]

testsuite: Fix up gcc.target/i386/sse4_1-stv-1.c test [PR113452]

From what I can see, this test has been written for a backend fix and
assumes the loop isn't vectorized (at least, it wasn't when the test was
added, it contains an early exit), but that is no longer true and because
of the vectorization it now contains an instruction which the test scans
for not being present.

I think we should just disable vectorization here.

2024-01-18  Jakub Jelinek  <jakub@redhat.com>

	PR testsuite/113452
	* gcc.target/i386/sse4_1-stv-1.c: Add -fno-tree-vectorize to
	dg-options.