drm/bridge: tc358764: drop drm_connector_(un)register

Drop drm_connector handling that is not needed:

- drm_dev_register() in the display controller driver takes
  care of registering connectors.
  So the call to drm_connector_register() call is not needed in the bridge
  driver.

- Use of drm_connector_unregister() is only required for drivers that
  explicit have called drm_dev_register.

- The reference counting using drm_connector_put() is likewise not needed.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Jonas Karlman <jonas@kwiboo.se>
Cc: Jernej Skrabec <jernej.skrabec@siol.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200726203324.3722593-4-sam@ravnborg.org