spi: dt-bindings: nuvoton,wpcm450-fiu: Fix warning in example (missing reg property)

Add missing "reg = <0>;" property to the flash@0 node in the example.

Fixes: dd71cd4dd6c9b ("spi: Add Nuvoton WPCM450 Flash Interface Unit (FIU) bindings")
Signed-off-by: Jonathan Neuschäfer <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

Documentation/devicetree/bindings/spi/nuvoton,wpcm450-fiu.yaml

···
 
       flash@0 {
         compatible = "jedec,spi-nor";
+        reg = <0>;
       };
     };