dt-bindings: can: fsl,flexcan: enable termination-* bindings

Enable termination-* binding and provide validation example for it.

Link: https://lore.kernel.org/r/20210818071232.20585-3-o.rempel@pengutronix.de


Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>