drm/bridge: ps8640: Let panel to set the connector type

The panel connector type should be set by the panel not the bridge, so
remove the connector_type assignment.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200416164404.2418426-2-enric.balletbo@collabora.com