media: rcar-isp: Parse named cs memory region

media: rcar-isp: Parse named cs memory region

Extend the device tree parsing to optionally parse the cs memory region
by name. The change is backward compatible with the device tree model
where a single unnamed region describes only the ISP channel select
function.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://lore.kernel.org/r/20250423163113.2961049-8-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>