cfg80211: simplify cfg80211_can_beacon_sec_chan API

Change cfg80211_can_beacon_sec_chan() to return true
if there is no secondary channel to simplify all the
current users of it. They all check the channel type
before calling the function because it returns false
if there's no secondary channel.

Also actually document the return value.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 0289d4c..a8496f4 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -3359,11 +3359,14 @@
 				 const u8 *frame, size_t len,
 				 int freq, int sig_dbm, gfp_t gfp);
 
-/*
+/**
  * cfg80211_can_beacon_sec_chan - test if ht40 on extension channel can be used
  * @wiphy: the wiphy
  * @chan: main channel
  * @channel_type: HT mode
+ *
+ * This function returns true if there is no secondary channel or the secondary
+ * channel can be used for beaconing (i.e. is not a radar channel etc.)
  */
 bool cfg80211_can_beacon_sec_chan(struct wiphy *wiphy,
 				  struct ieee80211_channel *chan,