dt-bindings: arm: Add Topwise A721

Add the bindings for Topwise A721 tablet
Signed-off-by: Pascal Roeleven <dev@pascalroeleven.nl>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210224105240.47754-2-dev@pascalroeleven.nl

Documentation/devicetree/bindings/arm/sunxi.yaml

@@ -802,6 +802,11 @@ properties:
           - const: tbs-biometrics,a711
           - const: allwinner,sun8i-a83t
 
+      - description: Topwise A721 Tablet
+        items:
+          - const: topwise,a721
+          - const: allwinner,sun4i-a10
+
       - description: Utoo P66
         items:
           - const: utoo,p66