rs6000: Add Power10 optimization for most _mm_movemask*

Power10 ISA added `vextract*` instructions which are realized in the
`vec_extractm` instrinsic.

Use `vec_extractm` for `_mm_movemask_ps`, `_mm_movemask_pd`, and
`_mm_movemask_epi8` compatibility intrinsics, when `_ARCH_PWR10`.

2021-11-29  Paul A. Clarke  <pc@us.ibm.com>

gcc
	* config/rs6000/xmmintrin.h (_mm_movemask_ps): Use vec_extractm
	when _ARCH_PWR10.
	* config/rs6000/emmintrin.h (_mm_movemask_pd): Likewise.
	(_mm_movemask_epi8): Likewise.