dt-bindings: arm: fsl: Add BSH SMM-M2 IMX6ULZ SystemMaster board

Add bindings for BSH SystemMaster (SMM) M2 IMX6ULZ board.
Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Documentation/devicetree/bindings/arm/fsl.yaml

@@ -670,6 +670,7 @@ properties:
       - description: i.MX6ULZ based Boards
         items:
           - enum:
+              - bsh,imx6ulz-bsh-smm-m2    # i.MX6 ULZ BSH SystemMaster
               - fsl,imx6ulz-14x14-evk     # i.MX6 ULZ 14x14 EVK Board
           - const: fsl,imx6ull # This seems odd. Should be last?
           - const: fsl,imx6ulz