drm/dp/mst: constify drm_dp_mst_topology_cbs structures

The drm_dp_mst_topology_cbs structures are never modified, so declare them
as const.

Done with the help of Coccinelle.
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp_mst.c

@@ -512,7 +512,7 @@ static void intel_dp_mst_hotplug(struct drm_dp_mst_topology_mgr *mgr)
 	drm_kms_helper_hotplug_event(dev);
 }
 
-static struct drm_dp_mst_topology_cbs mst_cbs = {
+static const struct drm_dp_mst_topology_cbs mst_cbs = {
 	.add_connector = intel_dp_add_mst_connector,
 	.register_connector = intel_dp_register_mst_connector,
 	.destroy_connector = intel_dp_destroy_mst_connector,

drivers/gpu/drm/radeon/radeon_dp_mst.c

@@ -329,7 +329,7 @@ static void radeon_dp_mst_hotplug(struct drm_dp_mst_topology_mgr *mgr)
 	drm_kms_helper_hotplug_event(dev);
 }
 
-struct drm_dp_mst_topology_cbs mst_cbs = {
+const struct drm_dp_mst_topology_cbs mst_cbs = {
 	.add_connector = radeon_dp_add_mst_connector,
 	.register_connector = radeon_dp_register_mst_connector,
 	.destroy_connector = radeon_dp_destroy_mst_connector,

include/drm/drm_dp_mst_helper.h

@@ -420,7 +420,7 @@ struct drm_dp_payload {
 struct drm_dp_mst_topology_mgr {
 
 	struct device *dev;
-	struct drm_dp_mst_topology_cbs *cbs;
+	const struct drm_dp_mst_topology_cbs *cbs;
 	int max_dpcd_transaction_bytes;
 	struct drm_dp_aux *aux; /* auxch for this topology mgr to use */
 	int max_payloads;