mac80211: declare ieee80211_ave_rssi as EXPORT

ieee80211_ave_rssi need to be declare as export for driver to use it.
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

@@ -3802,6 +3802,14 @@ 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);
 
+/**
+ * ieee80211_ave_rssi - report the average rssi for the specified interface
+ *
+ * @vif: the specified virtual interface
+ *
+ * This function return the average rssi value for the requested interface.
+ * It assumes that the given vif is valid.
+ */
 int ieee80211_ave_rssi(struct ieee80211_vif *vif);
 
 #endif /* MAC80211_H */

net/mac80211/util.c

@@ -1803,3 +1803,4 @@ int ieee80211_ave_rssi(struct ieee80211_vif *vif)
 
 	return ifmgd->ave_beacon_signal;
 }
+EXPORT_SYMBOL_GPL(ieee80211_ave_rssi);