net: mscc: ocelot: Fix uninitialized error in ocelot_netdevice_event()

With gcc-4.1.2:

    drivers/net/ethernet/mscc/ocelot.c: In function ‘ocelot_netdevice_event’:
    drivers/net/ethernet/mscc/ocelot.c:1129: warning: ‘ret’ may be used uninitialized in this function

If the list iterated over by netdev_for_each_lower_dev() is empty, ret
is never initialized, and converted into a notifier return value.

Fix this by preinitializing ret to zero.

Fixes: a556c76 ("net: mscc: Add initial Ocelot switch support")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mscc/ocelot.c

@@ -1126,7 +1126,7 @@ static int ocelot_netdevice_event(struct notifier_block *unused,
 {
 	struct netdev_notifier_changeupper_info *info = ptr;
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
-	int ret;
+	int ret = 0;
 
 	if (netif_is_lag_master(dev)) {
 		struct net_device *slave;