crypto: marvell/cesa - Improving code readability

When looking for available engines, the variable "engine" is
assigned to "&cesa->engines[i]" at the beginning of the for loop. Replacing
next occurences of "&cesa->engines[i]" by "engine" and in order to improve
readability.

Signed-off-by: Romain Perier <romain.perier@free-electrons.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>