Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/sh/kernel/nmi_debug.c b/arch/sh/kernel/nmi_debug.c
index 730d928..1177786 100644
--- a/arch/sh/kernel/nmi_debug.c
+++ b/arch/sh/kernel/nmi_debug.c
@@ -1,9 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2007 Atmel Corporation
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
  */
 #include <linux/delay.h>
 #include <linux/kdebug.h>