Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/net/wan/hdlc.c b/drivers/net/wan/hdlc.c
index 7221a53..dfc1677 100644
--- a/drivers/net/wan/hdlc.c
+++ b/drivers/net/wan/hdlc.c
@@ -1,12 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Generic HDLC support routines for Linux
  *
  * Copyright (C) 1999 - 2008 Krzysztof Halasa <khc@pm.waw.pl>
  *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of version 2 of the GNU General Public License
- * as published by the Free Software Foundation.
- *
  * Currently supported:
  *	* raw IP-in-HDLC
  *	* Cisco HDLC