drm: atmel-hlcdc: fix connector and encoder types

The hlcdc IP keep the pixel stream in raw RGB mode, and does not provide
any specific connector. Since DRM_MODE_CONNECTOR_RAW_RGB does not exist,
use DRM_MODE_CONNECTOR_Unknown.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Tested-by: Nicolas Ferre <nicolas.ferre@atmel.com>