staging: greybus: add SPDX identifiers to all greybus driver files

It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.

Update the drivers/staging/greybus files files with the correct SPDX
license identifier based on the license text in the file itself.  The
SPDX identifier is a legally binding shorthand, which can be used
instead of the full boiler plate text.

This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.

Cc: Vaibhav Hiremath <hvaibhav.linux@gmail.com>
Cc: "Bryan O'Donoghue" <pure.logic@nexus-software.ie>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Acked-by: Vaibhav Agarwal <vaibhav.sr@gmail.com>
Acked-by: David Lin <dtwlin@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Acked-by: Johan Hovold <johan@kernel.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Mark Greer <mgreer@animalcreek.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/greybus/Documentation/firmware/authenticate.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
 /*
  * Sample code to test CAP protocol
  *

drivers/staging/greybus/Documentation/firmware/firmware.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
 /*
  * Sample code to test firmware-management protocol
  *

drivers/staging/greybus/arche-apb-ctrl.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Arche Platform driver to control APB.
  *

drivers/staging/greybus/arche-platform.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Arche Platform driver to enable Unipro link.
  *

drivers/staging/greybus/arche_platform.h

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Arche Platform driver to enable Unipro link.
  *

drivers/staging/greybus/arpc.h

@@ -1,3 +1,4 @@
+// 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.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Greybus Audio Device Class Protocol helpers
  *

drivers/staging/greybus/audio_apbridgea.h

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: BSD-3-Clause
 /**
  * Copyright (c) 2015-2016 Google Inc.
  * All rights reserved.

drivers/staging/greybus/audio_codec.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * APBridge ALSA SoC dummy codec driver
  * Copyright 2016 Google Inc.

drivers/staging/greybus/audio_codec.h

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Greybus audio driver
  * Copyright 2015 Google Inc.

drivers/staging/greybus/audio_gb.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Greybus Audio Device Class Protocol helpers
  *

drivers/staging/greybus/audio_manager.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Greybus operations
  *

drivers/staging/greybus/audio_manager.h

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Greybus operations
  *

drivers/staging/greybus/audio_manager_module.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Greybus operations
  *

drivers/staging/greybus/audio_manager_private.h

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Greybus operations
  *

drivers/staging/greybus/audio_manager_sysfs.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Greybus operations
  *

drivers/staging/greybus/audio_module.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Greybus audio driver
  * Copyright 2015 Google Inc.

drivers/staging/greybus/audio_topology.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Greybus audio driver
  * Copyright 2015-2016 Google Inc.

drivers/staging/greybus/authentication.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Greybus Component Authentication Protocol (CAP) Driver.
  *

drivers/staging/greybus/bootrom.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * BOOTROM Greybus driver.
  *