mac80211: clean up station cleanup timer

We currently run this timer exactly once when
a new mac80211 device is registered, but that
is completely pointless since it will have no
work to do at all. Therefore, remove that and
also simplify some code using the timer.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 5ec0a7c5..999f8fb 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -768,9 +768,8 @@
 	if (!timer_needed)
 		return;
 
-	local->sta_cleanup.expires =
-		round_jiffies(jiffies + STA_INFO_CLEANUP_INTERVAL);
-	add_timer(&local->sta_cleanup);
+	mod_timer(&local->sta_cleanup,
+		  round_jiffies(jiffies + STA_INFO_CLEANUP_INTERVAL));
 }
 
 void sta_info_init(struct ieee80211_local *local)
@@ -783,14 +782,6 @@
 
 	setup_timer(&local->sta_cleanup, sta_info_cleanup,
 		    (unsigned long)local);
-	local->sta_cleanup.expires =
-		round_jiffies(jiffies + STA_INFO_CLEANUP_INTERVAL);
-}
-
-int sta_info_start(struct ieee80211_local *local)
-{
-	add_timer(&local->sta_cleanup);
-	return 0;
 }
 
 void sta_info_stop(struct ieee80211_local *local)