mac80211: fix memory leak

On error we jumped to the error label and returned the error code but we
missed releasing sinfo.

Fixes: 5fe74014172d ("mac80211: avoid excessive stack usage in sta_info")
Reviewed-by: NJulian Calaby <julian.calaby@gmail.com>
Signed-off-by: NSudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

net/mac80211/sta_info.c

@@ -562,6 +562,7 @@ static int sta_info_insert_finish(struct sta_info *sta) __acquires(RCU)
 	__cleanup_single_sta(sta);
  out_err:
 	mutex_unlock(&local->sta_mtx);
+	kfree(sinfo);
 	rcu_read_lock();
 	return err;
 }