net/mlx5e: Prevent adding the same vxlan port

Do not allow the same vxlan udp port to be added to the device more than
once.

Fixes: b3f63c3d ("net/mlx5e: Add netdev support for VXLAN tunneling")
Signed-off-by: NMatthew Finlay <matt@mellanox.com>
Signed-off-by: NSaeed Mahameed <saeedm@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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

@@ -105,6 +105,9 @@ static void mlx5e_vxlan_add_port(struct work_struct *work)
 	struct mlx5e_vxlan *vxlan;
 	int err;
 
+	if (mlx5e_vxlan_lookup_port(priv, port))
+		goto free_work;
+
 	if (mlx5e_vxlan_core_add_port_cmd(priv->mdev, port))
 		goto free_work;