soundwire: fix SPDX license for header files

No C++ comments in .h files
Reviewed-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NPierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/soundwire/bus.h

-// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
-// Copyright(c) 2015-17 Intel Corporation.
+/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
+/* Copyright(c) 2015-17 Intel Corporation. */
 
 #ifndef __SDW_BUS_H
 #define __SDW_BUS_H

drivers/soundwire/cadence_master.h

-// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
-// Copyright(c) 2015-17 Intel Corporation.
+/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
+/* Copyright(c) 2015-17 Intel Corporation. */
 #include <sound/soc.h>
 
 #ifndef __SDW_CADENCE_H

drivers/soundwire/intel.h

-// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
-// Copyright(c) 2015-17 Intel Corporation.
+/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
+/* Copyright(c) 2015-17 Intel Corporation. */
 
 #ifndef __SDW_INTEL_LOCAL_H
 #define __SDW_INTEL_LOCAL_H