dt-bindings: arm: imx: update fsl.yaml for imx8dxl

i.MX8DXL is a device targeting the automotive and industrial market
segments. The chip is designed to achieve both high performance and
low power consumption. It has a dual (2x) Cortex-A35 processor.

Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Documentation/devicetree/bindings/arm/fsl.yaml

@@ -1042,6 +1042,12 @@ properties:
               - toradex,colibri-imx8x     # Colibri iMX8X Modules
           - const: fsl,imx8qxp
 
+      - description: i.MX8DXL based Boards
+        items:
+          - enum:
+              - fsl,imx8dxl-evk           # i.MX8DXL EVK Board
+          - const: fsl,imx8dxl
+
       - description: i.MX8QXP Boards with Toradex Coilbri iMX8X Modules
         items:
           - enum: