mac80211: fix scan_sdata assignment

We need to use RCU to assign scan_sdata.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/scan.c

@@ -304,7 +304,7 @@ static void __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted,
 	if (local->scan_req != local->int_scan_req)
 		cfg80211_scan_done(local->scan_req, aborted);
 	local->scan_req = NULL;
-	local->scan_sdata = NULL;
+	rcu_assign_pointer(local->scan_sdata, NULL);
 
 	local->scanning = 0;
 	local->scan_channel = NULL;