greybus: add copyright statements

The Greybus audio source files included no copyright statements.
Add them.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/audio-dai.c

+/*
+ * Greybus audio Digital Audio Interface (DAI) driver
+ *
+ * Copyright 2015 Google Inc.
+ * Copyright 2015 Linaro Ltd.
+ *
+ * Released under the GPLv2 only.
+ */
+
 #include <linux/kernel.h>
 #include <linux/device.h>
 #include <linux/interrupt.h>

drivers/staging/greybus/audio-gb-cmds.c

+/*
+ * Greybus audio commands
+ *
+ * Copyright 2015 Google Inc.
+ * Copyright 2015 Linaro Ltd.
+ *
+ * Released under the GPLv2 only.
+ */
+
 #include <linux/kernel.h>
 
 #include "greybus.h"

drivers/staging/greybus/audio-pcm.c

+/*
+ * Greybus audio Pulse Code Modulation (PCM) driver
+ *
+ * Copyright 2015 Google Inc.
+ * Copyright 2015 Linaro Ltd.
+ *
+ * Released under the GPLv2 only.
+ */
+
 #include <linux/kernel.h>
 #include <linux/device.h>
 #include <linux/interrupt.h>

drivers/staging/greybus/audio.c

+/*
+ * Greybus audio driver
+ *
+ * Copyright 2015 Google Inc.
+ * Copyright 2015 Linaro Ltd.
+ *
+ * Released under the GPLv2 only.
+ */
+
 #include <linux/kernel.h>
 #include <linux/device.h>
 #include <linux/interrupt.h>

drivers/staging/greybus/audio.h

+/*
+ * Greybus audio
+ *
+ * Copyright 2015 Google Inc.
+ * Copyright 2015 Linaro Ltd.
+ *
+ * Released under the GPLv2 only.
+ */
+
 #ifndef __GB_AUDIO_H
 #define __GB_AUDIO_H
 #include <linux/kernel.h>