mac80211: fix sdata->radar_required locking

radar_required setting wasn't protected by
local->mtx in some places. This should prevent
from scanning/radar detection/roc colliding.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
index f43613a..42c6592 100644
--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -196,6 +196,8 @@
 {
 	struct ieee80211_sub_if_data *sdata;
 
+	lockdep_assert_held(&local->mtx);
+
 	rcu_read_lock();
 	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
 		if (sdata->radar_required) {