dsa: fix freeing of sparse port allocation

If we have defined a sparse port allocation which is non-contiguous and
contains gaps, the code freeing port_names will just stop when it
encouters a first NULL port_names, which is not right, we should iterate
over all possible number of ports (DSA_MAX_PORTS) until we are done.
Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/dsa.c

@@ -350,9 +350,11 @@ static void dsa_of_free_platform_data(struct dsa_platform_data *pd)
 
 	for (i = 0; i < pd->nr_chips; i++) {
 		port_index = 0;
-		while (pd->chip[i].port_names &&
-			pd->chip[i].port_names[++port_index])
+		while (port_index < DSA_MAX_PORTS) {
+			if (pd->chip[i].port_names[port_index])
 				kfree(pd->chip[i].port_names[port_index]);
+			port_index++;
+		}
 		kfree(pd->chip[i].rtable);
 	}
 	kfree(pd->chip);