drm/qxl: 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/qxl/qxl_drv.c

@@ -102,7 +102,7 @@ static int qxl_drm_freeze(struct drm_device *dev)
 
 	/* unpin the front buffers */
 	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
-		struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
+		const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
 		if (crtc->enabled)
 			(*crtc_funcs->disable)(crtc);
 	}