mac80211: add back lost debugfs files

Somehow these files were never present or lost, but the code
is there and they seem somewhat useful, so add them back.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/debugfs_sta.c

@@ -522,6 +522,7 @@ void ieee80211_sta_debugfs_add(struct sta_info *sta)
 		return;
 
 	DEBUGFS_ADD(flags);
+	DEBUGFS_ADD(aid);
 	DEBUGFS_ADD(num_ps_buf_frames);
 	DEBUGFS_ADD(last_seq_ctrl);
 	DEBUGFS_ADD(agg_status);