cfg80211: Provide an API to report NAN function termination

Provide a function that reports NAN DE function termination. The function
may be terminated due to one of the following reasons: user request,
ttl expiration or failure.
If the NAN instance is tied to the owner, the notification will be
sent to the socket that started the NAN interface only

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>