ALSA: sb16: constify snd_pcm_ops structures

snd_pcm_ops are not supposed to change at runtime. All functions
working with snd_pcm_ops provided by <sound/pcm.h> work with
const snd_pcm_ops. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/isa/sb/sb16_main.c

@@ -838,7 +838,7 @@ int snd_sb16dsp_configure(struct snd_sb * chip)
 	return 0;
 }
 
-static struct snd_pcm_ops snd_sb16_playback_ops = {
+static const struct snd_pcm_ops snd_sb16_playback_ops = {
 	.open =		snd_sb16_playback_open,
 	.close =	snd_sb16_playback_close,
 	.ioctl =	snd_pcm_lib_ioctl,
@@ -849,7 +849,7 @@ static struct snd_pcm_ops snd_sb16_playback_ops = {
 	.pointer =	snd_sb16_playback_pointer,
 };
 
-static struct snd_pcm_ops snd_sb16_capture_ops = {
+static const struct snd_pcm_ops snd_sb16_capture_ops = {
 	.open =		snd_sb16_capture_open,
 	.close =	snd_sb16_capture_close,
 	.ioctl =	snd_pcm_lib_ioctl,