drm_dp_mst_port_add_connector() directly calls the
drm_connector_register() now and
drm_dp_mst_topology_mgr_cbs.register_connector callback is not getting
called anymore.

Hence remove all drm_dp_mst_topology_mgr_cbs.register_connector
callbacks.

This is the preparatory step for removing the
drm_dp_mst_topology_mgr_cbs.register_connector callback hook.

The removal is done with below sementic patch:

@r1@
identifier func, E;
@@
struct drm_dp_mst_topology_cbs E = {
	...,
-        .register_connector = func
};

@delete depends on r1@
identifier r1.func;
@@
- static void func(...){...}
Signed-off-by: Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com>
Suggested-by: Emil Velikov <emil.velikov@collabora.com>
Suggested-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200307083023.76498-3-pankaj.laxminarayan.bharadiya@intel.comReviewed-by: Lyude Paul <lyude@redhat.com>