cfg80211: allow the user space to change current NAN configuration

Some NAN configuration paramaters may change during the operation of
the NAN device. For example, a user may want to update master preference
value when the device gets plugged/unplugged to the power.
Add API that allows to do so.

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>