Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/powerpc/boot/treeboot-walnut.c b/arch/powerpc/boot/treeboot-walnut.c
index 097974e..623f58e 100644
--- a/arch/powerpc/boot/treeboot-walnut.c
+++ b/arch/powerpc/boot/treeboot-walnut.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Old U-boot compatibility for Walnut
  *
@@ -6,10 +7,6 @@
  * Copyright 2007 IBM Corporation
  *   Based on cuboot-83xx.c, which is:
  * Copyright (c) 2007 Freescale Semiconductor, Inc.
- *
- * 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 "ops.h"