Merge branch 'netlink_multicast'

Johannes Berg says:

====================
netlink/genetlink cleanups & multicast improvements

I'm looking at using the multicast group functionality in a way that would
benefit from knowing when there are subscribers to avoid collecting the
required data when there aren't any. During this I noticed that the unbind
for multicast groups doesn't actually work - it's never called when sockets
are closed. Luckily, nobody actually uses the functionality.

While looking at the code trying to find why it's not called and where the
multicast listeners are actually removed, I found the potential cleanup in
patch 3. Patch 2 also has a cleanup for a generic netlink API in this area.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>