crypto: rockchip - rework by using crypto_engine

Instead of doing manual queue management, let's use the crypto/engine
for that.
In the same time, rework the requests handling to be easier to
understand (and fix all bugs related to them).

Fixes: ce0183cb

 ("crypto: rockchip - switch to skcipher API")
Reviewed-by: John Keeping <john@metanate.com>
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>