dt-bindings: arm64: dts: mediatek: Add mt8183-pumpkin board

Add binding documentation for the MT8183 Pumpkin board.

Signed-off-by: Fabien Parent <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Matthias Brugger <[e-mail]>

Documentation/devicetree/bindings/arm/mediatek.yaml

···
           - const: mediatek,mt8183
       - items:
           - enum:
+              - mediatek,mt8183-pumpkin
+          - const: mediatek,mt8183
+      - items:
+          - enum:
               - mediatek,mt8516-pumpkin
           - const: mediatek,mt8516