ALSA: mips: Constify snd_device_ops definitions

Now we may declare const for snd_device_ops definitions, so let's do
it for optimization.

There should be no functional changes by this patch.

Link: https://lore.kernel.org/r/20200103081714.9560-13-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/mips/hal2.c

@@ -732,7 +732,7 @@ static int hal2_dev_free(struct snd_device *device)
 	return 0;
 }
 
-static struct snd_device_ops hal2_ops = {
+static const struct snd_device_ops hal2_ops = {
 	.dev_free = hal2_dev_free,
 };
 

sound/mips/sgio2audio.c

@@ -787,7 +787,7 @@ static int snd_sgio2audio_dev_free(struct snd_device *device)
 	return snd_sgio2audio_free(chip);
 }
 
-static struct snd_device_ops ops = {
+static const struct snd_device_ops ops = {
 	.dev_free = snd_sgio2audio_dev_free,
 };