crypto: marvell/cesa - Handle zero-length skcipher requests

[ Upstream commit 8a4e047c6cc07676f637608a9dd675349b5de0a7 ]

Do not access random memory for zero-length skcipher requests.
Just return 0.

Fixes: f63601fd ("crypto: marvell/cesa - add a new driver for Marvell's CESA")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>