Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/irqchip/irq-ath79-cpu.c b/drivers/irqchip/irq-ath79-cpu.c
index befe93c..923e4bb 100644
--- a/drivers/irqchip/irq-ath79-cpu.c
+++ b/drivers/irqchip/irq-ath79-cpu.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  Atheros AR71xx/AR724x/AR913x specific interrupt handling
  *
@@ -7,10 +8,6 @@
  *  Copyright (C) 2008 Imre Kaloz <kaloz@openwrt.org>
  *
  *  Parts of this file are based on Atheros' 2.6.15/2.6.31 BSP
- *
- *  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/interrupt.h>