cfg80211: disallow more station changes

The following changes are invalid and should be
disallowed when a station already exists:
 * supported rates changes, except for TDLS peers
 * listen interval changes
 * HT capability changes

Disallow them and also update a mac80211 comment
explaining how they would be racy.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index f4d12c7..7d290bc 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1208,10 +1208,11 @@
 		sta->sta.aid = params->aid;
 
 	/*
-	 * FIXME: updating the following information is racy when this
-	 *	  function is called from ieee80211_change_station().
-	 *	  However, all this information should be static so
-	 *	  maybe we should just reject attemps to change it.
+	 * Some of the following updates would be racy if called on an
+	 * existing station, via ieee80211_change_station(). However,
+	 * all such changes are rejected by cfg80211 except for updates
+	 * changing the supported rates on an existing but not yet used
+	 * TDLS peer.
 	 */
 
 	if (params->listen_interval >= 0)