cfg80211: add start / stop NAN commands

This allows user space to start/stop NAN interface.
A NAN interface is like P2P device in a few aspects: it
doesn't have a netdev associated to it.
Add the new interface type and prevent operations that
can't be executed on NAN interface like scan.

Define several attributes that may be configured by user space
when starting NAN functionality (master preference and dual
band operation)

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>

net/mac80211/offchannel.c

@@ -838,6 +838,7 @@ int ieee80211_mgmt_tx(struct wiphy *wiphy, struct wireless_dev *wdev,
 	case NL80211_IFTYPE_P2P_DEVICE:
 		need_offchan = true;
 		break;
+	case NL80211_IFTYPE_NAN:
 	default:
 		return -EOPNOTSUPP;
 	}