[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/sound.c

@@ -387,8 +387,7 @@ int __init snd_minor_info_init(void)
 
 int __exit snd_minor_info_done(void)
 {
-	if (snd_minor_info_entry)
-		snd_info_unregister(snd_minor_info_entry);
+	snd_info_free_entry(snd_minor_info_entry);
 	return 0;
 }
 #endif /* CONFIG_PROC_FS */