docs: dt-bindings: add missing address/size-cells to example

Complete the example of recommended order of properties by adding
missing address/size-cells.  They are not necessary to illustrate the
style, but lack of them us bit really correct DTS code which might
confuse readers.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://lore.kernel.org/r/20240325091139.18602-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Rob Herring <robh@kernel.org>