dt-bindings: sram: sunxi-sram: add V3s compatible string

Add compatible string for V3s, with H3 one as fallback.

This is used in device tree now, but not standardized in DT binding.
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20201003235018.1121618-2-icenowy@aosc.ioSigned-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/devicetree/bindings/sram/allwinner,sun4i-a10-system-control.yaml

@@ -33,6 +33,9 @@ properties:
           - const: allwinner,sun4i-a10-system-control
       - const: allwinner,sun8i-a23-system-control
       - const: allwinner,sun8i-h3-system-control
+      - items:
+          - const: allwinner,sun8i-v3s-system-control
+          - const: allwinner,sun8i-h3-system-control
       - items:
           - const: allwinner,sun8i-r40-system-control
           - const: allwinner,sun4i-a10-system-control