net: dsa: lantiq_gswip: Fix start index in gswip_port_fdb()

The first N entries in priv->vlans are reserved for managing ports which
are not part of a bridge. Use priv->hw_info->max_ports to consistently
access per-bridge entries at index 7. Starting at
priv->hw_info->cpu_port (6) is harmless in this case because
priv->vlan[6].bridge is always NULL so the comparison result is always
false (which results in this entry being skipped).
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/lantiq_gswip.c

@@ -1360,7 +1360,7 @@ static int gswip_port_fdb(struct dsa_switch *ds, int port,
 	struct net_device *bridge = dsa_port_bridge_dev_get(dsa_to_port(ds, port));
 	struct gswip_priv *priv = ds->priv;
 	struct gswip_pce_table_entry mac_bridge = {0,};
-	unsigned int cpu_port = priv->hw_info->cpu_port;
+	unsigned int max_ports = priv->hw_info->max_ports;
 	int fid = -1;
 	int i;
 	int err;
@@ -1368,7 +1368,7 @@ static int gswip_port_fdb(struct dsa_switch *ds, int port,
 	if (!bridge)
 		return -EINVAL;
 
-	for (i = cpu_port; i < ARRAY_SIZE(priv->vlans); i++) {
+	for (i = max_ports; i < ARRAY_SIZE(priv->vlans); i++) {
 		if (priv->vlans[i].bridge == bridge) {
 			fid = priv->vlans[i].fid;
 			break;