rtc: maxim: Add SPDX license identifiers

Replace GPL v2.0+ license statements with SPDX license
identifiers.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
diff --git a/drivers/rtc/rtc-max8998.c b/drivers/rtc/rtc-max8998.c
index d8c0f9b..c873b45 100644
--- a/drivers/rtc/rtc-max8998.c
+++ b/drivers/rtc/rtc-max8998.c
@@ -1,16 +1,10 @@
-/*
- * RTC driver for Maxim MAX8998
- *
- * Copyright (C) 2010 Samsung Electronics Co.Ltd
- * Author: Minkyu Kang <mk7.kang@samsung.com>
- * Author: Joonyoung Shim <jy0922.shim@samsung.com>
- *
- *  This program is free software; you can redistribute  it and/or modify it
- *  under  the terms of  the GNU General  Public License as published by the
- *  Free Software Foundation;  either version 2 of the  License, or (at your
- *  option) any later version.
- *
- */
+// SPDX-License-Identifier: GPL-2.0+
+//
+// RTC driver for Maxim MAX8998
+//
+// Copyright (C) 2010 Samsung Electronics Co.Ltd
+// Author: Minkyu Kang <mk7.kang@samsung.com>
+// Author: Joonyoung Shim <jy0922.shim@samsung.com>
 
 #include <linux/module.h>
 #include <linux/i2c.h>