cfg80211: validate nl80211 station handling better

The nl80211 station handling code is a bit messy
and doesn't do a lot of validation. It seems like
this could be an issue for drivers that don't use
mac80211 to validate everything.

As cfg80211 doesn't keep station state, move the
validation of allowing supported_rates to change
for TDLS only in station mode to mac80211.

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 150c0ee..5eda593 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -1346,7 +1346,12 @@
  *
  * @add_station: Add a new station.
  * @del_station: Remove a station; @mac may be NULL to remove all stations.
- * @change_station: Modify a given station.
+ * @change_station: Modify a given station. Note that flags changes are not much
+ *	validated in cfg80211, in particular the auth/assoc/authorized flags
+ *	might come to the driver in invalid combinations -- make sure to check
+ *	them, also against the existing state! Also, supported_rates changes are
+ *	not checked in station mode -- drivers need to reject (or ignore) them
+ *	for anything but TDLS peers.
  * @get_station: get station information for the station identified by @mac
  * @dump_station: dump station callback -- resume dump at index @idx
  *