soundwire: intel: fix SPDX license for header file

Some more headers had C++ style SDPX line, fix that and change copyright
so that it is consistent with rest of the code in subsystem
Signed-off-by: NVinod Koul <vkoul@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/soundwire/sdw_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_H
 #define __SDW_INTEL_H