drm/omap: Determine connector type directly in omap_connector.c

Instead of determining the connector type from the type of the display's
omap_dss_device and passing it to the omap_connector_init() function,
move the type determination code to omap_connector.c and remove the type
argument to the connector init function. This moves code to a more
natural location, making the driver easier to read.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>