net: mscc: ocelot: allow offloading of bridge on top of LAG

The blamed commit was too aggressive, and it made ocelot_netdevice_event
react only to network interface events emitted for the ocelot switch
ports.

In fact, only the PRECHANGEUPPER should have had that check.

When we ignore all events that are not for us, we miss the fact that the
upper of the LAG changes, and the bonding interface gets enslaved to a
bridge. This is an operation we could offload under certain conditions.

Fixes: 7afb3e5 ("net: mscc: ocelot: don't handle netdev events for other netdevs")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210118135210.2666246-1-olteanv@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mscc/ocelot_net.c

@@ -1042,10 +1042,8 @@ static int ocelot_netdevice_event(struct notifier_block *unused,
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 	int ret = 0;
 
-	if (!ocelot_netdevice_dev_check(dev))
-		return 0;
-
 	if (event == NETDEV_PRECHANGEUPPER &&
+	    ocelot_netdevice_dev_check(dev) &&
 	    netif_is_lag_master(info->upper_dev)) {
 		struct netdev_lag_upper_info *lag_upper_info = info->upper_info;
 		struct netlink_ext_ack *extack;