media: rcar-vin: Improve error paths for parallel devices

Use the __free(fwnode_handle) hooks to free the endpoints when the
function exits to simplify the error paths and make the intent more
clear.

While at it correct the error message when failing to parse an endpoint
to report the correct node.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://lore.kernel.org/r/20250613153434.2001800-8-niklas.soderlund+renesas@ragnatech.se


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