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>
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index 621dfa1..a577762 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -211,6 +211,7 @@
 #define NETDEV_UNREGISTER_BATCH 0x0011
 #define NETDEV_BONDING_DESLAVE  0x0012
 #define NETDEV_NOTIFY_PEERS	0x0013
+#define NETDEV_JOIN		0x0014
 
 #define SYS_DOWN	0x0001	/* Notify of system down */
 #define SYS_RESTART	SYS_DOWN