ALSA: hwdep: Allow to assign the given parent

Just like PCM, allow hwdep to be assigned to a different parent device
than the card.  It'll be used for the HD-audio codec device in the
later patches.

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

include/sound/hwdep.h

@@ -68,6 +68,7 @@ struct snd_hwdep {
 	wait_queue_head_t open_wait;
 	void *private_data;
 	void (*private_free) (struct snd_hwdep *hwdep);
+	struct device *dev;
 	const struct attribute_group **groups;
 
 	struct mutex open_mutex;