mac80211: merge the upstream ht40 fix

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@24033 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/mac80211/patches/310-pending_work.patch

@@ -290,3 +290,16 @@
  	mutex_unlock(&reg_mutex);
  
  	return r;
+--- a/net/wireless/chan.c
++++ b/net/wireless/chan.c
+@@ -54,8 +54,10 @@ static bool can_beacon_sec_chan(struct w
+ 	switch (channel_type) {
+ 	case NL80211_CHAN_HT40PLUS:
+ 		diff = 20;
++		break;
+ 	case NL80211_CHAN_HT40MINUS:
+ 		diff = -20;
++		break;
+ 	default:
+ 		return false;
+ 	}