drm/rcar-du: Don't cast crtc to rcrtc twice in the same function

Reuse the previously cast variable instead.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_crtc.c

@@ -413,7 +413,7 @@ static int rcar_du_crtc_mode_set_base(struct drm_crtc *crtc, int x, int y,
 	rcrtc->plane->src_x = x;
 	rcrtc->plane->src_y = y;
 
-	rcar_du_crtc_update_base(to_rcar_crtc(crtc));
+	rcar_du_crtc_update_base(rcrtc);
 
 	return 0;
 }