rs6000.md (altivec_stvx): Add parallels to stvx.

        * config/rs6000/rs6000.md (altivec_stvx): Add parallels to stvx.
        (altivec_lvsl): Change constraint to b.
        (altivec_lvsr): Same.
        (altivec_lvebx): Same.
        (altivec_lvehx): Same.
        (altivec_lvewx): Same.
        (altivec_lvxl): Same.
        (altivec_lvx): Same.
        (altivec_stvx): Add parallel.
        (altivec_stvxl): Same.
        (altivec_stvehx): Same.
        (altivec_stvebx): Same.
        (altivec_stvebx): Same.

From-SVN: r48890