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>

drivers/gpu/drm/drm_edid.c

@@ -3361,7 +3361,7 @@ EXPORT_SYMBOL(drm_edid_to_speaker_allocation);
  * 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;

include/drm/drm_edid.h

@@ -326,7 +326,7 @@ void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid);
 int drm_edid_to_sad(struct edid *edid, struct cea_sad **sads);
 int drm_edid_to_speaker_allocation(struct edid *edid, u8 **sadb);
 int drm_av_sync_delay(struct drm_connector *connector,
-		      struct drm_display_mode *mode);
+		      const struct drm_display_mode *mode);
 struct drm_connector *drm_select_eld(struct drm_encoder *encoder);
 int drm_load_edid_firmware(struct drm_connector *connector);