ASoC: samsung: bells: Convert to SPDX License Identifier

Replace GPL v2.0 license statements with SPDX license identifier.
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/samsung/bells.c

-/*
- * Bells audio support
- *
- * Copyright 2012 Wolfson Microelectronics
- *
- * 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+
+//
+// Bells audio support
+//
+// Copyright 2012 Wolfson Microelectronics
 
 #include <sound/soc.h>
 #include <sound/soc-dapm.h>