crypto: atmel-aes - Reestablish the correct tfm context at dequeue

In case there were more requests from different tfms in the crypto
queue, only the context of the last initialized tfm was considered.

Fixes: ec2088b6 ("crypto: atmel-aes - Allocate aes dev at tfm init time")
Reported-by: Wolfgang Ocker <weo@reccoware.de>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>