gpu: ipu-v3: Assign of_node of child platform devices to corresponding ports

The crtc child device driver shouldn't have to modify the of_node of its
platform device in the probe function. Instead, let the IPU core driver
set the of_node when the platform device is created.

Also reorder the client_reg array so the elements are in port id order
(CSIs first, then DIs).

Suggested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>