ALSA: oxfw: enable to keep memory block for model-specific structure

ALSA oxfw driver should have backward compatibility to old
firewire-speakers driver. Additionally, in future commit, scs1x driver
will be merged. It's nice to add a pointer to have a memory block for
model-specific structures.

This commit adds a member to 'struct snd_oxfw' for this aim. Deallocation
is done at freeing ALSA card structure.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/oxfw/oxfw.h

@@ -74,6 +74,7 @@ struct snd_oxfw {
 	wait_queue_head_t hwdep_wait;
 
 	const struct ieee1394_device_id *entry;
+	void *spec;
 };
 
 /*