dt-bindings: arm: npcm: Add nuvoton,wpcm450 compatible string

The WPCM450 is an older BMC SoC in the Nuvoton NPCM family, originally
marketed as Winbond WPCM450.

Signed-off-by: Jonathan Neuschäfer <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Reviewed-by: Joel Stanley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Joel Stanley <[e-mail]>

Documentation/devicetree/bindings/arm/npcm/npcm.yaml

···
     const: '/'
   compatible:
     oneOf:
+      - description: WPCM450 based boards
+        items:
+          - enum:
+              - supermicro,x9sci-ln4f-bmc   # Supermicro X9SCI-LN4F server's BMC
+          - const: nuvoton,wpcm450
+
       - description: NPCM750 based boards
         items:
           - enum: