Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/x86/um/delay.c b/arch/x86/um/delay.c
index a8fb7ca..8d510ce 100644
--- a/arch/x86/um/delay.c
+++ b/arch/x86/um/delay.c
@@ -1,10 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 2011 Richard Weinberger <richrd@nod.at>
  * Mostly copied from arch/x86/lib/delay.c
- *
- * 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/export.h>