Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/iio/dac/ad5755.c b/drivers/iio/dac/ad5755.c
index 2d03cc8..b9175fb 100644
--- a/drivers/iio/dac/ad5755.c
+++ b/drivers/iio/dac/ad5755.c
@@ -1,9 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * AD5755, AD5755-1, AD5757, AD5735, AD5737 Digital to analog converters driver
  *
  * Copyright 2012 Analog Devices Inc.
- *
- * Licensed under the GPL-2.
  */
 
 #include <linux/device.h>