crypto: sahara - handle zero-length aes requests

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

Fixes: 5de8875 ("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>

Author: opanait-wr

drivers/crypto/sahara.c

@@ -674,6 +674,9 @@ static int sahara_aes_crypt(struct skcipher_request *req, unsigned long mode)
 	struct sahara_dev *dev = dev_ptr;
 	int err = 0;
 
+	if (!req->cryptlen)
+		return 0;
+
 	if (unlikely(ctx->keylen != AES_KEYSIZE_128))
 		return sahara_aes_fallback(req, mode);