[ALSA] Fix Oops at rmmod with CONFIG_SND_VERBOSE_PROCFS=n

Fixed Oops at rmmod with CONFIG_SND_VERBOSE_PROCFS=n.
Add ifdef to struct fields for optimization and better compile
checks.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/pcm_memory.c b/sound/core/pcm_memory.c
index a0119ae..428f8c1 100644
--- a/sound/core/pcm_memory.c
+++ b/sound/core/pcm_memory.c
@@ -100,8 +100,10 @@
 int snd_pcm_lib_preallocate_free(struct snd_pcm_substream *substream)
 {
 	snd_pcm_lib_preallocate_dma_free(substream);
+#ifdef CONFIG_SND_VERBOSE_PROCFS
 	snd_info_unregister(substream->proc_prealloc_entry);
 	substream->proc_prealloc_entry = NULL;
+#endif
 	return 0;
 }
 
@@ -124,7 +126,7 @@
 	return 0;
 }
 
-#ifdef CONFIG_PROC_FS
+#ifdef CONFIG_SND_VERBOSE_PROCFS
 /*
  * read callback for prealloc proc file
  *
@@ -203,9 +205,9 @@
 	substream->proc_prealloc_entry = entry;
 }
 
-#else /* !CONFIG_PROC_FS */
+#else /* !CONFIG_SND_VERBOSE_PROCFS */
 #define preallocate_info_init(s)
-#endif
+#endif /* CONFIG_SND_VERBOSE_PROCFS */
 
 /*
  * pre-allocate the buffer and create a proc file for the substream