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>
diff --git a/include/drm/drm_encoder_slave.h b/include/drm/drm_encoder_slave.h
index 2f65633..7dc3852 100644
--- a/include/drm/drm_encoder_slave.h
+++ b/include/drm/drm_encoder_slave.h
@@ -54,7 +54,7 @@
 	void (*save)(struct drm_encoder *encoder);
 	void (*restore)(struct drm_encoder *encoder);
 	bool (*mode_fixup)(struct drm_encoder *encoder,
-			   struct drm_display_mode *mode,
+			   const struct drm_display_mode *mode,
 			   struct drm_display_mode *adjusted_mode);
 	int (*mode_valid)(struct drm_encoder *encoder,
 			  struct drm_display_mode *mode);