batman-adv: update copyright years for 2015

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
diff --git a/net/batman-adv/gateway_client.h b/net/batman-adv/gateway_client.h
index 7ee53bb..185fb08 100644
--- a/net/batman-adv/gateway_client.h
+++ b/net/batman-adv/gateway_client.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2009-2014 B.A.T.M.A.N. contributors:
+/* Copyright (C) 2009-2015 B.A.T.M.A.N. contributors:
  *
  * Marek Lindner
  *