dt-bindings: mtd: st,spear600-smi: #address/size-cells is mandatory

These properties must be set because they overwrite the default values,
especially #size-cells which is 0 for most controllers and is 'const: 1'
here.

Fixes: 68cd8ef484 ("dt-bindings: mtd: st,spear600-smi: convert to DT schema")
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Documentation/devicetree/bindings/mtd/st,spear600-smi.yaml

@@ -60,6 +60,8 @@ required:
   - compatible
   - reg
   - clock-rate
+  - "#address-cells"
+  - "#size-cells"
 
 unevaluatedProperties: false