drm: Make the .mode_fixup() operations mode argument a const pointer

The passed mode must not be modified by the operation, make it const.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/nouveau/nv04_dac.c

@@ -332,7 +332,7 @@ nv17_dac_detect(struct drm_encoder *encoder, struct drm_connector *connector)
 }
 
 static bool nv04_dac_mode_fixup(struct drm_encoder *encoder,
-				struct drm_display_mode *mode,
+				const struct drm_display_mode *mode,
 				struct drm_display_mode *adjusted_mode)
 {
 	if (nv04_dac_in_use(encoder))