drm/exynos: Constify exynos_drm_crtc_ops

The Exynos DRM code does not modify the ops provided by CRTC driver in
exynos_drm_crtc_create() call.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>
Reviewed-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.h b/drivers/gpu/drm/exynos/exynos_drm_drv.h
index 44f128a..0e95122 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_drv.h
+++ b/drivers/gpu/drm/exynos/exynos_drm_drv.h
@@ -226,7 +226,7 @@
 	unsigned int			dpms;
 	wait_queue_head_t		pending_flip_queue;
 	struct drm_pending_vblank_event	*event;
-	struct exynos_drm_crtc_ops	*ops;
+	const struct exynos_drm_crtc_ops	*ops;
 	void				*ctx;
 };