dt-bindings: arm: fsl: add Plymovent M2M board

Add Plymovent Group BV M2M iMX6dl based board

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>