dt-bindings: arm: add TQMa8MPxL board

TQMa8MPxL is a SOM family using NXP i.MX8MP CPU family
MBa8MPxL is an evaluation mainbord for this SOM

The SOM needs a mainboard, therefore we provide two compatibles here:

"tq,imx8mp-<SOM>" for the module and
"tq,imx8mp-<SOM>-<SBC>"

Signed-off-by: Markus Niebel <Markus.Niebel@tq-group.com>
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>