We can now probe devices with device tree only configuration using
ti-sysc interconnect target module driver. Let's configure the
module, but keep the legacy "ti,hwmods" peroperty until the child
devices are probing with ti-sysc interconnect driver.

Initially let's just update the top level dss node to probe with ti-sysc
interconnect target module driver. The child nodes are still children
of dispc, only the node indentation changes for them now along with
using the reg range provided by top level dss.

Cc: Jyri Sarha <jsarha@ti.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>