ALSA: ac97: add an ac97 bus

AC97 is a bus for sound usage. It enables for a AC97 AC-Link to link one
controller to 0 to 4 AC97 codecs.

The goal of this new implementation is to implement a device/driver
model for AC97, with an automatic scan of the bus and automatic
discovery of AC97 codec devices.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/ac97/codec.c

@@ -0,0 +1,15 @@
+/*
+ *  Copyright (C) 2016 Robert Jarzmik <robert.jarzmik@free.fr>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <sound/ac97_codec.h>
+#include <sound/ac97/codec.h>
+#include <sound/ac97/controller.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <sound/soc.h>	/* For compat_ac97_* */
+