[ALSA] Fix disconnection of proc interface

- Add the linked list to each proc entry to enable a single-shot
  disconnection (unregister)
- Deprecate snd_info_unregister(), use snd_info_free_entry()
- Removed NULL checks of snd_info_free_entry()

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>

sound/core/seq/seq_device.c

@@ -573,7 +573,7 @@ static void __exit alsa_seq_device_exit(void)
 {
 	remove_drivers();
 #ifdef CONFIG_PROC_FS
-	snd_info_unregister(info_entry);
+	snd_info_free_entry(info_entry);
 #endif
 	if (num_ops)
 		snd_printk(KERN_ERR "drivers not released (%d)\n", num_ops);