crypto: cfb - fix decryption

crypto_cfb_decrypt_segment() incorrectly XOR'ed generated keystream with
IV, rather than with data stream, resulting in incorrect decryption.
Test vectors will be added in the next patch.
Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/cfb.c

@@ -144,7 +144,7 @@ static int crypto_cfb_decrypt_segment(struct skcipher_walk *walk,
 
 	do {
 		crypto_cfb_encrypt_one(tfm, iv, dst);
-		crypto_xor(dst, iv, bsize);
+		crypto_xor(dst, src, bsize);
 		iv = src;
 
 		src += bsize;