dt-bindings: arm: bcm2835: Add Raspberry Pi 400 to DT schema

Add new Raspberry Pi 400 to DT schema.
Signed-off-by: NStefan Wahren <stefan.wahren@i2se.com>
Acked-by: NRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1622981777-5023-5-git-send-email-stefan.wahren@i2se.comSigned-off-by: NNicolas Saenz Julienne <nsaenz@kernel.org>

Documentation/devicetree/bindings/arm/bcm/bcm2835.yaml

@@ -18,6 +18,7 @@ properties:
       - description: BCM2711 based Boards
         items:
           - enum:
+              - raspberrypi,400
               - raspberrypi,4-model-b
           - const: brcm,bcm2711