dt-bindings: arm: fsl: add imx8qm boards compatible string

Add imx8qm boards compatible string

Cc: devicetree@vger.kernel.org
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Documentation/devicetree/bindings/arm/fsl.yaml

@@ -764,6 +764,12 @@ properties:
           - const: zii,imx8mq-ultra
           - const: fsl,imx8mq
 
+      - description: i.MX8QM based Boards
+        items:
+          - enum:
+              - fsl,imx8qm-mek           # i.MX8QM MEK Board
+          - const: fsl,imx8qm
+
       - description: i.MX8QXP based Boards
         items:
           - enum: