dt-bindings: arm: fsl: add compatible string for Kobo Clara HD

This adds a compatible string for the Kobo Clara HD eBook reader.
Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Documentation/devicetree/bindings/arm/fsl.yaml

@@ -164,6 +164,7 @@ properties:
         items:
           - enum:
               - fsl,imx6sll-evk
+              - kobo,clarahd
           - const: fsl,imx6sll
 
       - description: i.MX6SX based Boards