dt-bindings: usb: samsung-hsotg: remove bindings already part of dwc2

samsung,s3c6400-hsotg compatible is already fully covered in dwc2.yaml
bindings.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230722201620.35489-1-krzysztof.kozlowski@linaro.org


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