[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>
diff --git a/sound/core/pcm_memory.c b/sound/core/pcm_memory.c
index 067d205..be030cb 100644
--- a/sound/core/pcm_memory.c
+++ b/sound/core/pcm_memory.c
@@ -101,7 +101,7 @@
 {
 	snd_pcm_lib_preallocate_dma_free(substream);
 #ifdef CONFIG_SND_VERBOSE_PROCFS
-	snd_info_unregister(substream->proc_prealloc_entry);
+	snd_info_free_entry(substream->proc_prealloc_entry);
 	substream->proc_prealloc_entry = NULL;
 #endif
 	return 0;