cfg80211: vastly simplify locking

Virtually all code paths in cfg80211 already (need to) hold
the RTNL. As such, there's little point in having another
four mutexes for various parts of the code, they just cause
lock ordering issues (and much of the time, the RTNL and a
few of the others need thus be held.)

Simplify all this by getting rid of the extra four mutexes
and just use the RTNL throughout. Only a few code changes
were needed to do this and we can get rid of a work struct
for bonus points.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/wireless/mlme.c b/net/wireless/mlme.c
index c21e32f..68b40f2 100644
--- a/net/wireless/mlme.c
+++ b/net/wireless/mlme.c
@@ -313,14 +313,14 @@
 {
 	int err;
 
-	mutex_lock(&rdev->devlist_mtx);
+	ASSERT_RTNL();
+
 	wdev_lock(dev->ieee80211_ptr);
 	err = __cfg80211_mlme_auth(rdev, dev, chan, auth_type, bssid,
 				   ssid, ssid_len, ie, ie_len,
 				   key, key_len, key_idx,
 				   sae_data, sae_data_len);
 	wdev_unlock(dev->ieee80211_ptr);
-	mutex_unlock(&rdev->devlist_mtx);
 
 	return err;
 }
@@ -424,12 +424,12 @@
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
 	int err;
 
-	mutex_lock(&rdev->devlist_mtx);
+	ASSERT_RTNL();
+
 	wdev_lock(wdev);
 	err = __cfg80211_mlme_assoc(rdev, dev, chan, bssid,
 				    ssid, ssid_len, req);
 	wdev_unlock(wdev);
-	mutex_unlock(&rdev->devlist_mtx);
 
 	return err;
 }
@@ -844,7 +844,7 @@
 			    dfs_update_channels_wk);
 	wiphy = &rdev->wiphy;
 
-	mutex_lock(&cfg80211_mutex);
+	rtnl_lock();
 	for (bandid = 0; bandid < IEEE80211_NUM_BANDS; bandid++) {
 		sband = wiphy->bands[bandid];
 		if (!sband)
@@ -877,7 +877,7 @@
 			check_again = true;
 		}
 	}
-	mutex_unlock(&cfg80211_mutex);
+	rtnl_unlock();
 
 	/* reschedule if there are other channels waiting to be cleared again */
 	if (check_again)