Merge branch 'vxlan_lower_dev_unregister'

Daniel Borkmann says:

====================
vxlan updates

Did the split into two patches upon request from Cong Wang.

Changelog:

 v1->v2:
  - Removed BUG_ON as it's not needed.
 v2->v3:
  - Removed dev->reg_state check for netns.
 v3->v4:
  - Removed list_del(), we seem to do it in some places and
    in some others not; we agreed it's not really necessary.
  - Split patch into 2 patches, notifier part and module
    unload cleanup part.
====================

Reviewed-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: David S. Miller <davem@davemloft.net>