net: dsa: sja1105: exit sja1105_vlan_filtering when called multiple times

VLAN filtering is a global property for sja1105, and that means that we
rely on the DSA core to not call us more than once.

But we need to introduce some per-port state for the tagger, namely the
xmit_tpid, and the best place to do that is where the xmit_tpid changes,
namely in sja1105_vlan_filtering. So at the moment, exit early from the
function to avoid unnecessarily resetting the switch for each port call.
Then we'll change the xmit_tpid prior to the early exit in the next
patch.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/sja1105/sja1105_main.c

@@ -2158,6 +2158,9 @@ static int sja1105_vlan_filtering(struct dsa_switch *ds, int port, bool enabled)
 	else
 		state = SJA1105_VLAN_FILTERING_FULL;
 
+	if (priv->vlan_state == state)
+		return 0;
+
 	priv->vlan_state = state;
 
 	table = &priv->static_config.tables[BLK_IDX_GENERAL_PARAMS];