staging: greybus: correct SPDX License Identifier

Replace SPDX License Identifier comments with C comments.
Reported by checkpatch.
Signed-off-by: Ioannis Valasakis <code@wizofe.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/greybus/arche_platform.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Arche Platform driver to enable Unipro link.
  *

drivers/staging/greybus/arpc.h

-// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
+/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
 /*
  * This file is provided under a dual BSD/GPLv2 license.  When using or
  * redistributing this file, you may do so under either license.

drivers/staging/greybus/audio_apbridgea.h

-// SPDX-License-Identifier: BSD-3-Clause
+/* SPDX-License-Identifier: BSD-3-Clause */
 /**
  * Copyright (c) 2015-2016 Google Inc.
  * All rights reserved.

drivers/staging/greybus/audio_codec.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Greybus audio driver
  * Copyright 2015 Google Inc.

drivers/staging/greybus/audio_manager.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Greybus operations
  *

drivers/staging/greybus/audio_manager_private.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Greybus operations
  *

drivers/staging/greybus/bundle.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Greybus bundles
  *

drivers/staging/greybus/connection.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Greybus connections
  *