The NEON code replicates too closely the SSE code, including
a masked 16-bits shift. But NEON, like AltiVec (#9539), has
unsigned 8-bits shift, so use that instead and drop the masking.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Romain Dolbeau <romain.dolbeau@european-processor-initiative.eu>
Closes#9725