dt-bindings: arm: amlogic: add Amlogic AD401 bindings

Add the compatible for the Amlogic A1 Based AD401 board.
Signed-off-by: Jianxin Pan <jianxin.pan@amlogic.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

Documentation/devicetree/bindings/arm/amlogic.yaml

@@ -159,5 +159,7 @@ properties:
 
       - description: Boards with the Amlogic Meson A1 A113L SoC
         items:
+          - enum:
+              - amlogic,ad401
           - const: amlogic,a1
 ...