drm/exynos: constify all struct drm_*_helper funcs pointers

They are not to be modified.

Generated using the semantic patch:

@@
@@
(
  const struct drm_crtc_helper_funcs *
|
- struct drm_crtc_helper_funcs *
+ const struct drm_crtc_helper_funcs *
)

@@
@@
(
  const struct drm_encoder_helper_funcs *
|
- struct drm_encoder_helper_funcs *
+ const struct drm_encoder_helper_funcs *
)

@@
@@
(
  const struct drm_connector_helper_funcs *
|
- struct drm_connector_helper_funcs *
+ const struct drm_connector_helper_funcs *
)

@@
@@
(
  const struct drm_plane_helper_funcs *
|
- struct drm_plane_helper_funcs *
+ const struct drm_plane_helper_funcs *
)

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/exynos/exynos_hdmi.c

@@ -2101,7 +2101,7 @@ static void hdmi_dpms(struct exynos_drm_display *display, int mode)
 	struct hdmi_context *hdata = display_to_hdmi(display);
 	struct drm_encoder *encoder = hdata->encoder;
 	struct drm_crtc *crtc = encoder->crtc;
-	struct drm_crtc_helper_funcs *funcs = NULL;
+	const struct drm_crtc_helper_funcs *funcs = NULL;
 
 	DRM_DEBUG_KMS("mode %d\n", mode);