mac80211: remove final sta_info_flush()

When all interfaces have been removed, there can't
be any stations left over, so there's no need to
flush again. Remove this, and all code associated
with it, which also simplifies the function.

Tested-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/sta_info.h

@@ -548,8 +548,7 @@ void sta_info_recalc_tim(struct sta_info *sta);
 
 void sta_info_init(struct ieee80211_local *local);
 void sta_info_stop(struct ieee80211_local *local);
-int sta_info_flush(struct ieee80211_local *local,
-		   struct ieee80211_sub_if_data *sdata);
+int sta_info_flush(struct ieee80211_sub_if_data *sdata);
 void sta_set_rate_info_tx(struct sta_info *sta,
 			  const struct ieee80211_tx_rate *rate,
 			  struct rate_info *rinfo);