x86: replace/correct bogus "prefix_extra"

In the rdrand and rdseed cases "prefix_0f" is meant instead. For
mmx_floatv2siv2sf2 1 is correct only for the first alternative. For
the integer min/max cases 1 uniformly applies to legacy and VEX
encodings (the UB and SW variants are dealt with separately anyway).
Same for {,V}MOVNTDQA.

Unlike {,V}PEXTRW, which has two encoding forms, {,V}PINSRW only has
a single form in 0f space. (In *vec_extract<mode> note that the
dropped part if the condition also referenced non-existing alternative
2.)

Of the integer compare insns, only the 64-bit element forms are encoded
in 0f38 space.

gcc/

	* config/i386/i386.md (@rdrand<mode>): Add "prefix_0f". Drop
	"prefix_extra".
	(@rdseed<mode>): Likewise.
	* config/i386/mmx.md (<code><mode>3 [smaxmin and umaxmin cases]):
	Adjust "prefix_extra".
	* config/i386/sse.md (@vec_set<mode>_0): Likewise.
	(*sse4_1_<code><mode>3<mask_name>): Likewise.
	(*avx2_eq<mode>3): Likewise.
	(avx2_gt<mode>3): Likewise.
	(<sse2p4_1>_pinsr<ssemodesuffix>): Likewise.
	(*vec_extract<mode>): Likewise.
	(<vi8_sse4_1_avx2_avx512>_movntdqa): Likewise.