rtc: s5m: Add SPDX license identifier

Replace GPL v2.0+ license statement with SPDX license
identifier.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-s5m.c

@@ -1,19 +1,9 @@
-/*
- * Copyright (c) 2013-2014 Samsung Electronics Co., Ltd
- *	http://www.samsung.com
- *
- *  Copyright (C) 2013 Google, Inc
- *
- *  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.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- */
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Copyright (c) 2013-2014 Samsung Electronics Co., Ltd
+//	http://www.samsung.com
+//
+//  Copyright (C) 2013 Google, Inc
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt