cfg80211: annotate cfg80211_inform_bss

This function returns a referenced BSS struct
(or NULL), annotate with __must_check. It seems
that a lot of drivers get this completely wrong
and leak all BSS structs as a result.
Reported-by: Adam Mikuta <Adam.Mikuta@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/cfg80211.h

@@ -2636,8 +2636,10 @@ void cfg80211_sched_scan_stopped(struct wiphy *wiphy);
  *
  * This informs cfg80211 that BSS information was found and
  * the BSS should be updated/added.
+ *
+ * NOTE: Returns a referenced struct, must be released with cfg80211_put_bss()!
  */
-struct cfg80211_bss*
+struct cfg80211_bss * __must_check
 cfg80211_inform_bss_frame(struct wiphy *wiphy,
 			  struct ieee80211_channel *channel,
 			  struct ieee80211_mgmt *mgmt, size_t len,
@@ -2659,8 +2661,10 @@ cfg80211_inform_bss_frame(struct wiphy *wiphy,
  *
  * This informs cfg80211 that BSS information was found and
  * the BSS should be updated/added.
+ *
+ * NOTE: Returns a referenced struct, must be released with cfg80211_put_bss()!
  */
-struct cfg80211_bss*
+struct cfg80211_bss * __must_check
 cfg80211_inform_bss(struct wiphy *wiphy,
 		    struct ieee80211_channel *channel,
 		    const u8 *bssid,