ALSA: nm256: constify snd_ac97_res_table

snd_ac97_res_table are not supposed to change at runtime. All functions
working with snd_ac97_res_table provided by <sound/ac97_codec.h> work with
const snd_ac97_res_table. 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/nm256/nm256.c

@@ -1271,7 +1271,7 @@ snd_nm256_ac97_write(struct snd_ac97 *ac97,
 }
 
 /* static resolution table */
-static struct snd_ac97_res_table nm256_res_table[] = {
+static const struct snd_ac97_res_table nm256_res_table[] = {
 	{ AC97_MASTER, 0x1f1f },
 	{ AC97_HEADPHONE, 0x1f1f },
 	{ AC97_MASTER_MONO, 0x001f },