[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/oss/seq_oss.c

@@ -303,8 +303,7 @@ register_proc(void)
 static void
 unregister_proc(void)
 {
-	if (info_entry)
-		snd_info_unregister(info_entry);
+	snd_info_free_entry(info_entry);
 	info_entry = NULL;
 }
 #endif /* CONFIG_PROC_FS */