drm: Make drm_av_sync_delay() 'mode' argument const

drm_av_sync_delay() doesn't change the passed in mode, so make it const.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index e32218f..d895556 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -3361,7 +3361,7 @@
  * the sink doesn't support audio or video.
  */
 int drm_av_sync_delay(struct drm_connector *connector,
-		      struct drm_display_mode *mode)
+		      const struct drm_display_mode *mode)
 {
 	int i = !!(mode->flags & DRM_MODE_FLAG_INTERLACE);
 	int a, v;