ASoC: ak5558: Fix style for SPDX identifier

Use // for .c and /* for .h files according to:
Documentation/process/license-rules.rst file.
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/ak5558.c

 // SPDX-License-Identifier: GPL-2.0
-/*
- * Audio driver for AK5558 ADC
- *
- * Copyright (C) 2015 Asahi Kasei Microdevices Corporation
- * Copyright 2018 NXP
- */
+//
+// Audio driver for AK5558 ADC
+//
+// Copyright (C) 2015 Asahi Kasei Microdevices Corporation
+// Copyright 2018 NXP
 
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>

sound/soc/codecs/ak5558.h

-// SPDX-License-Identifier: GPL-2.0
-/*
+/* SPDX-License-Identifier: GPL-2.0
+ *
  * Audio driver header for AK5558
  *
  * Copyright (C) 2016 Asahi Kasei Microdevices Corporation