dt-bindings: altera: document Arria 10 based board compatibles

Add new compatible for Arria 10 based boards.
Signed-off-by: NKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: NDinh Nguyen <dinguyen@kernel.org>

Documentation/devicetree/bindings/arm/altera.yaml

@@ -23,6 +23,9 @@ properties:
 
       - description: Arria 10 boards
         items:
+          - enum:
+              - altr,socfpga-arria10-socdk
+              - enclustra,mercury-aa1
           - const: altr,socfpga-arria10
           - const: altr,socfpga