crypto: sun8i-ce - split into prepare/run/unprepare

This patch split the do_one_request into three.
Prepare will handle all DMA mapping and initialisation of the task
structure.
Unprepare will clean all DMA mapping.
And the do_one_request will be limited to just executing the task.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>