crypto: sahara - handle zero-length aes requests

[ Upstream commit d1d6351e ]

In case of a zero-length input, exit gracefully from sahara_aes_crypt().

Fixes: 5de88752 ("crypto: sahara - Add driver for SAHARA2 accelerator.")
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>