ALSA: hda - Make snd_hda_bus_type public

Define the common hd-audio driver and device types to bind over
snd_hda_bus_type publicly.  This allows to implement other type of
device and driver code over hd-audio bus.

Now both struct hda_codec and struct hda_codec_driver inherit these
new struct hdac_device and struct hdac_driver, respectively.

The bus registration is done in subsys_initcall() to assure it
before any other driver registrations.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_codec.c

@@ -1294,6 +1294,7 @@ int snd_hda_codec_new(struct hda_bus *bus, struct snd_card *card,
 	dev_set_name(dev, "hdaudioC%dD%d", card->number, codec_addr);
 	dev_set_drvdata(dev, codec); /* for sysfs */
 	device_enable_async_suspend(dev);
+	codec->core.type = HDA_DEV_LEGACY;
 
 	codec->bus = bus;
 	codec->card = card;