drm: bridge: dw-hdmi: 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.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: https://patchwork.freedesktop.org/patch/msgid/44c0ccab8b5658d17a3ed553e721136b53d95521.1502264156.git.arvind.yadav.cs@gmail.com

drivers/gpu/drm/bridge/synopsys/dw-hdmi-ahb-audio.c

@@ -517,7 +517,7 @@ static snd_pcm_uframes_t dw_hdmi_pointer(struct snd_pcm_substream *substream)
 	return bytes_to_frames(runtime, dw->buf_offset);
 }
 
-static struct snd_pcm_ops snd_dw_hdmi_ops = {
+static const struct snd_pcm_ops snd_dw_hdmi_ops = {
 	.open = dw_hdmi_open,
 	.close = dw_hdmi_close,
 	.ioctl = snd_pcm_lib_ioctl,