drm/udl: Init connector before encoder and CRTC

To mimic simple-pipe, we initialize the connector before the rest of
the display pipeline.

v2:
	* remove unnecessary calls to drm_connector_{register,unregister}()

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191210084905.5570-2-tzimmermann@suse.de