net/mlx5: Fix a NULL vs IS_ERR() check

The mlx5_esw_offloads_devlink_port() function returns error pointers, not
NULL.

Fixes: 7bef147 ("net/mlx5: Don't skip vport check")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/en_rep.c

@@ -1497,7 +1497,7 @@ mlx5e_vport_vf_rep_load(struct mlx5_core_dev *dev, struct mlx5_eswitch_rep *rep)
 
 	dl_port = mlx5_esw_offloads_devlink_port(dev->priv.eswitch,
 						 rpriv->rep->vport);
-	if (dl_port) {
+	if (!IS_ERR(dl_port)) {
 		SET_NETDEV_DEVLINK_PORT(netdev, dl_port);
 		mlx5e_rep_vnic_reporter_create(priv, dl_port);
 	}