dt-bindings: arm: fsl: Add the pico-pi-imx8m board

Add an entry for TechNexion PICO-PI-IMX8M board based on i.MX8MQ SoC
Datasheet can be found at:
https://s3.us-east-2.amazonaws.com/technexion/datasheets/picopiimx8m.pdf

Cc: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Andra Danciu <andradanciu1997@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Documentation/devicetree/bindings/arm/fsl.yaml

@@ -220,6 +220,7 @@ properties:
           - enum:
               - fsl,imx8mq-evk            # i.MX8MQ EVK Board
               - purism,librem5-devkit     # Purism Librem5 devkit
+              - technexion,pico-pi-imx8m  # TechNexion PICO-PI-8M evk
           - const: fsl,imx8mq
 
       - description: i.MX8QXP based Boards