dt-bindings: arm: fsl: add toradex,verdin-imx8mp et al.

Add toradex,verdin-imx8mp for the Verdin iMX8M Plus modules, its nonwifi
and wifi variants and the carrier boards (both Dahlia and the Verdin
Development Board) they may be mated in.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>