crypto: marvell/cesa - remove unneeded condition

creq->cache[] is an array inside the struct, it's not a pointer and it
can't be NULL.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>