drm/gma500: 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>
Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/gma500/oaktrail_crtc.c

@@ -483,7 +483,7 @@ static int oaktrail_crtc_mode_set(struct drm_crtc *crtc,
 
 	/* Flush the plane changes */
 	{
-		struct drm_crtc_helper_funcs *crtc_funcs =
+		const struct drm_crtc_helper_funcs *crtc_funcs =
 		    crtc->helper_private;
 		crtc_funcs->mode_set_base(crtc, x, y, old_fb);
 	}