mac80211: make ieee80211_beacon_connection_loss_work static

There's no need to declare the function in the
header file since it's only used in a single
place, so make it static.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index b9cb8db..ddb2db5 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1720,7 +1720,7 @@
 	mutex_unlock(&local->mtx);
 }
 
-void ieee80211_beacon_connection_loss_work(struct work_struct *work)
+static void ieee80211_beacon_connection_loss_work(struct work_struct *work)
 {
 	struct ieee80211_sub_if_data *sdata =
 		container_of(work, struct ieee80211_sub_if_data,