mac80211: handle operating mode notif in beacon/assoc response

In beacons and association response frames an AP may include an
operating mode notification element to advertise changes in the
number of spatial streams it can receive. Handle this using the
existing function that handles the action frame, but only handle
NSS changes, not bandwidth changes which aren't allowed here.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ieee80211_i.h

@@ -1197,6 +1197,7 @@ struct ieee802_11_elems {
 	u8 *pwr_constr_elem;
 	u8 *quiet_elem;	/* first quite element */
 	u8 *timeout_int;
+	u8 *opmode_notif;
 
 	/* length of them, respectively */
 	u8 ssid_len;
@@ -1435,7 +1436,7 @@ enum ieee80211_sta_rx_bandwidth ieee80211_sta_cur_vht_bw(struct sta_info *sta);
 void ieee80211_sta_set_rx_nss(struct sta_info *sta);
 void ieee80211_vht_handle_opmode(struct ieee80211_sub_if_data *sdata,
 				 struct sta_info *sta, u8 opmode,
-				 enum ieee80211_band band);
+				 enum ieee80211_band band, bool nss_only);
 
 /* Spectrum management */
 void ieee80211_process_measurement_req(struct ieee80211_sub_if_data *sdata,