x86: Enable FMA in rsqrt<mode>2 expander

x86: Enable FMA in rsqrt<mode>2 expander

Enable FMA in rsqrt<mode>2 expander and fold rsqrtv16sf2 expander into
rsqrt<mode>2 expander which expands to UNSPEC_RSQRT28 for TARGET_AVX512ER.
Although it doesn't show performance change in our workloads, FMA can
improve other workloads.

gcc/

	PR target/88713
	* config/i386/i386-expand.c (ix86_emit_swsqrtsf): Enable FMA.
	* config/i386/sse.md (VF_AVX512VL_VF1_128_256): New.
	(rsqrt<mode>2): Replace VF1_128_256 with VF_AVX512VL_VF1_128_256.
	(rsqrtv16sf2): Removed.

gcc/testsuite/

	PR target/88713
	* gcc.target/i386/pr88713-1.c: New test.
	* gcc.target/i386/pr88713-2.c: Likewise.