net/mlx5e: Fix possible use-after-free deleting fdb rule

After neigh-update-add failure we are still with a slow path rule but
the driver always assume the rule is an fdb rule.
Fix neigh-update-del by checking slow path tc flag on the flow.
Also fix neigh-update-add for when neigh-update-del fails the same.

Fixes: 5dbe906f ("net/mlx5e: Use a slow path rule instead if vxlan neighbour isn't available")
Signed-off-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_encap.c

@@ -147,7 +147,7 @@ void mlx5e_tc_encap_flows_add(struct mlx5e_priv *priv,
 	mlx5e_rep_queue_neigh_stats_work(priv);
 
 	list_for_each_entry(flow, flow_list, tmp_list) {
-		if (!mlx5e_is_offloaded_flow(flow))
+		if (!mlx5e_is_offloaded_flow(flow) || !flow_flag_test(flow, SLOW))
 			continue;
 		attr = flow->attr;
 		esw_attr = attr->esw_attr;
@@ -188,7 +188,7 @@ void mlx5e_tc_encap_flows_del(struct mlx5e_priv *priv,
 	int err;
 
 	list_for_each_entry(flow, flow_list, tmp_list) {
-		if (!mlx5e_is_offloaded_flow(flow))
+		if (!mlx5e_is_offloaded_flow(flow) || flow_flag_test(flow, SLOW))
 			continue;
 		attr = flow->attr;
 		esw_attr = attr->esw_attr;