ALSA: constify functions in ac97

Signed-off-by: Hanno Boeck <hanno@hboeck.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/include/sound/ac97_codec.h b/include/sound/ac97_codec.h
index 4940045..b602f47 100644
--- a/include/sound/ac97_codec.h
+++ b/include/sound/ac97_codec.h
@@ -477,7 +477,7 @@
 
 struct snd_ac97 {
 	/* -- lowlevel (hardware) driver specific -- */
-	struct snd_ac97_build_ops * build_ops;
+	const struct snd_ac97_build_ops *build_ops;
 	void *private_data;
 	void (*private_free) (struct snd_ac97 *ac97);
 	/* --- */