dt-bindings: arm: Add Topwise A721

Add the bindings for Topwise A721 tablet

Signed-off-by: Pascal Roeleven <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Maxime Ripard <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/arm/sunxi.yaml

···
           - 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