ALSA: opl4: Fix / cleanup ifdef CONFIG_PROC_FS

Some are replaced with the new ifdef CONFIG_SND_PROC_FS.  Some are
removed by building opl4_proc.o conditionally.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/drivers/opl4/opl4_local.h

@@ -178,7 +178,7 @@ struct snd_opl4 {
 	spinlock_t reg_lock;
 	struct snd_card *card;
 
-#ifdef CONFIG_PROC_FS
+#ifdef CONFIG_SND_PROC_FS
 	struct snd_info_entry *proc_entry;
 	int memory_access;
 #endif
@@ -207,10 +207,13 @@ void snd_opl4_write_memory(struct snd_opl4 *opl4, const char *buf, int offset, i
 /* opl4_mixer.c */
 int snd_opl4_create_mixer(struct snd_opl4 *opl4);
 
-#ifdef CONFIG_PROC_FS
+#ifdef CONFIG_SND_PROC_FS
 /* opl4_proc.c */
 int snd_opl4_create_proc(struct snd_opl4 *opl4);
 void snd_opl4_free_proc(struct snd_opl4 *opl4);
+#else
+static inline int snd_opl4_create_proc(struct snd_opl4 *opl4) { return 0; }
+static inline void snd_opl4_free_proc(struct snd_opl4 *opl4) {}
 #endif
 
 /* opl4_seq.c */