mac80211: check for non-managed interface

Average beacon signal only keep tracked by managed interface,
give warning and return 0 for the others.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/util.c

@@ -1801,6 +1801,10 @@ int ieee80211_ave_rssi(struct ieee80211_vif *vif)
 	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
 	struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
 
+	if (WARN_ON_ONCE(sdata->vif.type != NL80211_IFTYPE_STATION)) {
+		/* non-managed type inferfaces */
+		return 0;
+	}
 	return ifmgd->ave_beacon_signal;
 }
 EXPORT_SYMBOL_GPL(ieee80211_ave_rssi);