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_crtc_helper.h b/include/drm/drm_crtc_helper.h
index 7988e55..e01cc80 100644
--- a/include/drm/drm_crtc_helper.h
+++ b/include/drm/drm_crtc_helper.h
@@ -62,7 +62,7 @@
 
 	/* Provider can fixup or change mode timings before modeset occurs */
 	bool (*mode_fixup)(struct drm_crtc *crtc,
-			   struct drm_display_mode *mode,
+			   const struct drm_display_mode *mode,
 			   struct drm_display_mode *adjusted_mode);
 	/* Actually set the mode */
 	int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
@@ -96,7 +96,7 @@
 	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);
 	void (*prepare)(struct drm_encoder *encoder);
 	void (*commit)(struct drm_encoder *encoder);