net: In unregister_netdevice_notifier unregister the netdevices.
We already synthesize events in register_netdevice_notifier and synthesizing
events in unregister_netdevice_notifier allows to us remove the need for
special case cleanup code.
This change should be safe as it adds no new cases for existing callers
of unregiser_netdevice_notifier to handle.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: David S. Miller <davem@davemloft.net>