netpoll: disable netpoll when enslave a device

V3: rename NETDEV_ENSLAVE to NETDEV_JOIN

Currently we do nothing when we enslave a net device which is running netconsole.
Neil pointed out that we may get weird results in such case, so let's disable
netpoll on the device being enslaved. I think it is too harsh to prevent
the device being ensalved if it is running netconsole.

By the way, this patch also removes the NETDEV_GOING_DOWN from netconsole
netdev notifier, because netpoll will check if the device is running or not
and we don't handle NETDEV_PRE_UP neither.

This patch is based on net-next-2.6.

Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: Neil Horman <nhorman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -1640,6 +1640,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 		}
 	}
 
+	call_netdevice_notifiers(NETDEV_JOIN, slave_dev);
+
 	/* If this is the first slave, then we need to set the master's hardware
 	 * address to be the same as the slave's. */
 	if (is_zero_ether_addr(bond->dev->dev_addr))