mptcp: use SHA256_BLOCK_SIZE, not SHA_MESSAGE_BYTES

In preparation for naming the SHA-1 stuff in <linux/cryptohash.h>
properly and moving it to a more appropriate header, fix the HMAC-SHA256
code in mptcp_crypto_hmac_sha() to use SHA256_BLOCK_SIZE instead of
"SHA_MESSAGE_BYTES" which is actually the SHA-1 block size.
(Fortunately these are both 64 bytes, so this wasn't a "real" bug...)

Cc: Paolo Abeni <pabeni@redhat.com>
Cc: mptcp@lists.01.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

net/mptcp/crypto.c

@@ -61,7 +61,7 @@ void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac)
 	put_unaligned_be64(key2, key2be);
 
 	/* Generate key xored with ipad */
-	memset(input, 0x36, SHA_MESSAGE_BYTES);
+	memset(input, 0x36, SHA256_BLOCK_SIZE);
 	for (i = 0; i < 8; i++)
 		input[i] ^= key1be[i];
 	for (i = 0; i < 8; i++)
@@ -78,7 +78,7 @@ void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac)
 	sha256_final(&state, &input[SHA256_BLOCK_SIZE]);
 
 	/* Prepare second part of hmac */
-	memset(input, 0x5C, SHA_MESSAGE_BYTES);
+	memset(input, 0x5C, SHA256_BLOCK_SIZE);
 	for (i = 0; i < 8; i++)
 		input[i] ^= key1be[i];
 	for (i = 0; i < 8; i++)