dt-bindings: interconnect: sunxi: Add R40 MBUS compatible

The R40 MBUS compatible was introduced recently but it was never
documented.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20210901091852.479202-26-maxime@cerno.tech

Documentation/devicetree/bindings/arm/sunxi/allwinner,sun4i-a10-mbus.yaml

@@ -30,6 +30,7 @@ properties:
     enum:
       - allwinner,sun5i-a13-mbus
       - allwinner,sun8i-h3-mbus
+      - allwinner,sun8i-r40-mbus
       - allwinner,sun50i-a64-mbus
 
   reg: