dt-bindings: phy: hisilicon,hi3670-usb3: simplify example

syscon and simple-mfd cannot be used without device specific compatible,
so simplify the example to fix this.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Acked-By: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20220817142246.828762-3-krzysztof.kozlowski@linaro.org


Signed-off-by: Rob Herring <robh@kernel.org>