tcp: correctly crypto_alloc_hash return check

crypto_alloc_hash never returns NULL
Signed-off-by: NInsu Yun <wuninsu@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tcp.c

@@ -2950,7 +2950,7 @@ static void __tcp_alloc_md5sig_pool(void)
 			struct crypto_hash *hash;
 
 			hash = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
-			if (IS_ERR_OR_NULL(hash))
+			if (IS_ERR(hash))
 				return;
 			per_cpu(tcp_md5sig_pool, cpu).md5_desc.tfm = hash;
 		}