mac80211: clean up station flags debugfs

Avoid the really strange %s%s%s expression, use an array
of flag names and check that all flags are present.

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

net/mac80211/sta_info.h

@@ -69,6 +69,8 @@
  * @WLAN_STA_MPSP_RECIPIENT: local STA is recipient of a MPSP.
  * @WLAN_STA_PS_DELIVER: station woke up, but we're still blocking TX
  *	until pending frames are delivered
+ *
+ * @NUM_WLAN_STA_FLAGS: number of defined flags
  */
 enum ieee80211_sta_info_flags {
 	WLAN_STA_AUTH,
@@ -97,6 +99,8 @@ enum ieee80211_sta_info_flags {
 	WLAN_STA_MPSP_OWNER,
 	WLAN_STA_MPSP_RECIPIENT,
 	WLAN_STA_PS_DELIVER,
+
+	NUM_WLAN_STA_FLAGS,
 };
 
 #define ADDBA_RESP_INTERVAL HZ