[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/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index a7567b8..ac990bf 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -2214,7 +2214,7 @@
 	return 0;
 }
 
-#ifdef CONFIG_PROC_FS
+#ifdef CONFIG_SND_VERBOSE_PROCFS
 /*
  *  /proc interface
  */
@@ -2368,10 +2368,10 @@
 		}
 	}
 }
-#else /* !CONFIG_PROC_FS */
+#else /* !CONFIG_SND_VERBOSE_PROCFS */
 #define snd_pcm_oss_proc_init(pcm)
 #define snd_pcm_oss_proc_done(pcm)
-#endif /* CONFIG_PROC_FS */
+#endif /* CONFIG_SND_VERBOSE_PROCFS */
 
 /*
  *  ENTRY functions