drm/tilcdc: Remove obsolete drm_connector_register() calls

Remove obsolete drm_connector_register() calls from tilcdc_panel.c and
tilcdc_tfp410.c. All connectors are registered when drm_dev_register()
is called.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>