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/include/sound/jack.h b/include/sound/jack.h
index 6b013c6..f236e42 100644
--- a/include/sound/jack.h
+++ b/include/sound/jack.h
@@ -50,6 +50,8 @@
 	int type;
 	const char *id;
 	char name[100];
+	void *private_data;
+	void (*private_free)(struct snd_jack *);
 };
 
 #ifdef CONFIG_SND_JACK