cfg80211: Document update_ft_ies() cfg80211_ops

This was forgotten from the commit that added support for FT
operations with drivers that implement SME.
Signed-off-by: Jouni Malinen <j@w1.fi>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -1998,6 +1998,10 @@ struct cfg80211_update_ft_ies_params {
  *	advertise the support for MAC based ACL have to implement this callback.
  *
  * @start_radar_detection: Start radar detection in the driver.
+ *
+ * @update_ft_ies: Provide updated Fast BSS Transition information to the
+ *	driver. If the SME is in the driver/firmware, this information can be
+ *	used in building Authentication and Reassociation Request frames.
  */
 struct cfg80211_ops {
 	int	(*suspend)(struct wiphy *wiphy, struct cfg80211_wowlan *wow);