crypto: rockchip - Don't dequeue the request when device is busy

The device can only process one request at a time. So if multiple
requests came at the same time, we can enqueue them first, and
dequeue them one by one when the device is idle.

Signed-off-by: zain wang <wzz@rock-chips.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>