dt-bindings: display: bridge: renesas,dsi-csi2-tx: Allow panel@ subnode

dt-bindings: display: bridge: renesas,dsi-csi2-tx: Allow panel@ subnode

This controller can have both bridges and panels connected to it. In
order to describe panels properly in DT, pull in dsi-controller.yaml
and disallow only unevaluatedProperties, because the panel node is
optional. Include example binding with panel.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://lore.kernel.org/r/20250904210147.186728-4-marek.vasut+renesas@mailbox.org