dt-bindings: arm: Add i.MX8M Mini Toradex Verdin based Menlo board

Add DT compatible string for board based on the Toradex Verdin iMX8M
Mini SoM, the MX8Menlo. The board is a compatible replacement for
i.MX53 M53Menlo and features USB, multiple UARTs, ethernet, LEDs,
SD and eMMC.

Acked-by: Peng Fan <peng.fan@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@denx.de>
Cc: Francesco Dolcini <francesco.dolcini@toradex.com>
Cc: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: devicetree@vger.kernel.org
To: linux-arm-kernel@lists.infradead.org
Signed-off-by: Shawn Guo <shawnguo@kernel.org>