ALSA: core: 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/20200103081714.9560-5-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/hwdep.c

@@ -353,7 +353,7 @@ int snd_hwdep_new(struct snd_card *card, char *id, int device,
 {
 	struct snd_hwdep *hwdep;
 	int err;
-	static struct snd_device_ops ops = {
+	static const struct snd_device_ops ops = {
 		.dev_free = snd_hwdep_dev_free,
 		.dev_register = snd_hwdep_dev_register,
 		.dev_disconnect = snd_hwdep_dev_disconnect,