mac80211: add function retrieve average rssi

Add utility function to provide the average rssi per vif
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/mac80211.h

@@ -3801,4 +3801,7 @@ int ieee80211_add_srates_ie(struct ieee80211_vif *vif,
 
 int ieee80211_add_ext_srates_ie(struct ieee80211_vif *vif,
 				struct sk_buff *skb, bool need_basic);
+
+int ieee80211_ave_rssi(struct ieee80211_vif *vif);
+
 #endif /* MAC80211_H */

net/mac80211/util.c

@@ -1793,3 +1793,11 @@ int ieee80211_add_ext_srates_ie(struct ieee80211_vif *vif,
 	}
 	return 0;
 }
+
+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;
+
+	return ifmgd->ave_beacon_signal;
+}