net: pass info struct via netdevice notifier

So far, only net_device * could be passed along with netdevice notifier
event. This patch provides a possibility to pass custom structure
able to provide info that event listener needs to know.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>

v2->v3: fix typo on simeth
	shortened dev_getter
	shortened notifier_info struct name
v1->v2: fix notifier_call parameter in call_netdevice_notifier()
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/netxen/netxen_nic_main.c

@@ -3311,7 +3311,7 @@ static int netxen_netdev_event(struct notifier_block *this,
 				 unsigned long event, void *ptr)
 {
 	struct netxen_adapter *adapter;
-	struct net_device *dev = (struct net_device *)ptr;
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 	struct net_device *orig_dev = dev;
 	struct net_device *slave;