ALSA: intel8x0: constify ac97_pcm structures

ac97_pcm are not supposed to change at runtime. All functions
working with ac97_pcm provided by <sound/ac97_codec.h> work with
const ac97_pcm. So mark the non-const structs as const.
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/intel8x0.c

@@ -1721,7 +1721,7 @@ static void snd_intel8x0_mixer_free_ac97(struct snd_ac97 *ac97)
 	chip->ac97[ac97->num] = NULL;
 }
 
-static struct ac97_pcm ac97_pcm_defs[] = {
+static const struct ac97_pcm ac97_pcm_defs[] = {
 	/* front PCM */
 	{
 		.exclusive = 1,