Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/iio/dac/ad5593r.c b/drivers/iio/dac/ad5593r.c
index fc11ea0..44ea3b8 100644
--- a/drivers/iio/dac/ad5593r.c
+++ b/drivers/iio/dac/ad5593r.c
@@ -1,10 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * AD5593R Digital <-> Analog converters driver
  *
  * Copyright 2015-2016 Analog Devices Inc.
  * Author: Paul Cercueil <paul.cercueil@analog.com>
- *
- * Licensed under the GPL-2.
  */
 
 #include "ad5592r-base.h"