usb: gadget: f_uac2: 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: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/function/u_audio.c

@@ -354,7 +354,7 @@ static int uac_pcm_null(struct snd_pcm_substream *substream)
 	return 0;
 }
 
-static struct snd_pcm_ops uac_pcm_ops = {
+static const struct snd_pcm_ops uac_pcm_ops = {
 	.open = uac_pcm_open,
 	.close = uac_pcm_null,
 	.ioctl = snd_pcm_lib_ioctl,