ALSA: atiixp: 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: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/atiixp.c

@@ -1183,7 +1183,7 @@ static const struct snd_pcm_ops snd_atiixp_spdif_ops = {
 	.pointer =	snd_atiixp_pcm_pointer,
 };
 
-static struct ac97_pcm atiixp_pcm_defs[] = {
+static const struct ac97_pcm atiixp_pcm_defs[] = {
 	/* front PCM */
 	{
 		.exclusive = 1,