media: rcar-vin: Prepare for unifying all v4l-async notifiers

The R-Car VIN driver is needlessly complex and uses more then one
v4l-async notifier to attach to all its subdevices. Prepare for unifying
them by moving rvin_parallel_parse_of() to where it needs to be when
they are unified.

The function is moved verbatim and there is no change in behavior.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Tested-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://lore.kernel.org/r/20250613153434.2001800-7-niklas.soderlund+renesas@ragnatech.se


Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>