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>