Optimize v4si broadcast for noavx512vl.

This will enable below

-       vbroadcastss    .LC1(%rip), %xmm0
+       movl    $-45, %edx
+       vmovd   %edx, %xmm0
+       vpshufd $0, %xmm0, %xmm0

According to microbenchmark, it's faster than broadcast from memory
for TARGET_INTER_UNIT_MOVES_TO_VEC.

gcc/ChangeLog:

	* config/i386/sse.md (*vec_dupv4si): Disable memory operand
	for !TARGET_INTER_UNIT_MOVES_TO_VEC when prefer_for_speed.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr100865-8a.c: Adjust testcase.
	* gcc.target/i386/pr100865-8c.c: Ditto.
	* gcc.target/i386/pr100865-9c.c: Ditto.