ALSA: pci: 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/20200103081714.9560-10-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/azt3328.c b/sound/pci/azt3328.c
index b36e7a6..810d577 100644
--- a/sound/pci/azt3328.c
+++ b/sound/pci/azt3328.c
@@ -2355,7 +2355,7 @@ snd_azf3328_create(struct snd_card *card,
 {
 	struct snd_azf3328 *chip;
 	int err;
-	static struct snd_device_ops ops = {
+	static const struct snd_device_ops ops = {
 		.dev_free =     snd_azf3328_dev_free,
 	};
 	u8 dma_init;