bonding: Fix netconsole to not deadlock on rmmod

Netconsole calls netpoll_cleanup on receipt of a NETDEVICE_UNREGISTER event.
The notifier subsystem calls these event handlers with rtnl_lock held, which
netpoll_cleanup also takes, resulting in deadlock.  Fix this by calling the
__netpoll_cleanup interior function instead, and fixing up the additional
pointers.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>