net/mlxfw: fix a NULL dereference

If we hit this error path we end up returning ERR_PTR(0) which is NULL.
The caller is not expecting that so it results in a NULL dereference.

Fixes: 410ed13cae39 ("Add the mlxfw module for Mellanox firmware flash process")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Yotam Gigi <yotamg@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2.c

@@ -594,6 +594,7 @@ mlxfw_mfa2_file_component_get(const struct mlxfw_mfa2_file *mfa2_file,
 	if (memcmp(comp_data->buff, mlxfw_mfa2_comp_magic,
 		   mlxfw_mfa2_comp_magic_len) != 0) {
 		pr_err("Component has wrong magic\n");
+		err = -EINVAL;
 		goto err_out;
 	}