net/mlx5e: Fix free peer_flow when refcount is 0

It could be neigh update flow took a refcount on peer flow so
sometimes we cannot release peer flow even if parent flow is
being freed now.

Fixes: 5a7e5bcb ("net/mlx5e: Extend tc flow struct with reference counter")
Signed-off-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Eli Britstein <elibr@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

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

@@ -1626,8 +1626,11 @@ static void __mlx5e_tc_del_fdb_peer_flow(struct mlx5e_tc_flow *flow)
 
 	flow_flag_clear(flow, DUP);
 
-	mlx5e_tc_del_fdb_flow(flow->peer_flow->priv, flow->peer_flow);
-	kfree(flow->peer_flow);
+	if (refcount_dec_and_test(&flow->peer_flow->refcnt)) {
+		mlx5e_tc_del_fdb_flow(flow->peer_flow->priv, flow->peer_flow);
+		kfree(flow->peer_flow);
+	}
+
 	flow->peer_flow = NULL;
 }