ALSA: add private_data to struct snd_jack

Added private_data and private_free fields to struct snd_jack so that
the caller can assign the data.  It'll be helpful for avoiding the
double-free of the jack instance.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/jack.c b/sound/core/jack.c
index c8254c6..d54d1a0 100644
--- a/sound/core/jack.c
+++ b/sound/core/jack.c
@@ -35,6 +35,9 @@
 {
 	struct snd_jack *jack = device->device_data;
 
+	if (jack->private_free)
+		jack->private_free(jack);
+
 	/* If the input device is registered with the input subsystem
 	 * then we need to use a different deallocator. */
 	if (jack->registered)