fold-vec-splat-8.c: Add vspltisb to expected output.

fold-vec-splat-8.c: Add vspltisb to expected output.

[testsuite]
2017-11-29  Will Schmidt  <will_schmidt@vnet.ibm.com>

    * gcc.target/powerpc/fold-vec-splat-8.c: Add vspltisb to expected output.
    * gcc.target/powerpc/fold-vec-splats-int.c: Add mtvsrws to expected output.
    * gcc.target/powerpc/fold-vec-splats-longlong.c: Add mtvsrdd to expected output.

From-SVN: r255251