ALSA: hda: Constify snd_kcontrol_new items

Most of snd_kcontrol_new definitions are read-only and passed as-is.
Let's declare them as const for further optimization.

There should be no functional changes by this patch.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Takashi Iwai <[e-mail]>

sound/pci/hda/hda_codec.c

···
 	return change;
 }
 
-static struct snd_kcontrol_new dig_mixes[] = {
+static const struct snd_kcontrol_new dig_mixes[] = {
 	{
 		.access = SNDRV_CTL_ELEM_ACCESS_READ,
 		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
···
 {
 	int err;
 	struct snd_kcontrol *kctl;
-	struct snd_kcontrol_new *dig_mix;
+	const struct snd_kcontrol_new *dig_mix;
 	int idx = 0;
 	int val = 0;
 	const int spdif_index = 16;
···
 	return 0;
 }
 
-static struct snd_kcontrol_new dig_in_ctls[] = {
+static const struct snd_kcontrol_new dig_in_ctls[] = {
 	{
 		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
 		.name = SNDRV_CTL_NAME_IEC958("", CAPTURE, SWITCH),
···
 {
 	int err;
 	struct snd_kcontrol *kctl;
-	struct snd_kcontrol_new *dig_mix;
+	const struct snd_kcontrol_new *dig_mix;
 	int idx;
 
 	idx = find_empty_mixer_ctl_idx(codec, "IEC958 Capture Switch", 0);

sound/pci/hda/patch_sigmatel.c

···
 	struct sigmatel_spec *spec = codec->spec;
 	u32 caps = query_amp_caps(codec, nid, HDA_OUTPUT);
 	struct snd_kcontrol_new *knew;
-	static struct snd_kcontrol_new abeep_mute_ctl =
+	static const struct snd_kcontrol_new abeep_mute_ctl =
 		HDA_CODEC_MUTE(NULL, 0, 0, 0);
-	static struct snd_kcontrol_new dbeep_mute_ctl =
+	static const struct snd_kcontrol_new dbeep_mute_ctl =
 		HDA_CODEC_MUTE_BEEP(NULL, 0, 0, 0);
-	static struct snd_kcontrol_new beep_vol_ctl =
+	static const struct snd_kcontrol_new beep_vol_ctl =
 		HDA_CODEC_VOLUME(NULL, 0, 0, 0);
 
 	/* check for mute support for the the amp */