arm64: dts: zynqmp: Add ports for the DisplayPort subsystem

The DPSUB DT bindings now specify ports to model the connections with
the programmable logic and the DisplayPort output. Add them to the
device tree.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Michal Simek <michal.simek@amd.com>