dt-bindings: arm: imx: Add the i.MX6SX-SDB Rev-A board

Add board binding for i.MX6SX-SDB Rev-A board which is already
supported.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Documentation/devicetree/bindings/arm/fsl.yaml

@@ -172,6 +172,7 @@ properties:
           - enum:
               - fsl,imx6sx-sabreauto      # i.MX6 SoloX Sabre Auto Board
               - fsl,imx6sx-sdb            # i.MX6 SoloX SDB Board
+              - fsl,imx6sx-sdb-reva       # i.MX6 SoloX SDB Rev-A Board
           - const: fsl,imx6sx
 
       - description: i.MX6UL based Boards