spi: dt-bindings: samsung: drop cs-gpios

Remove cs-gpios because it is already mentioned by common
spi-controller.yaml.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230601095908.563865-2-krzysztof.kozlowski@linaro.org


Signed-off-by: Mark Brown <broonie@kernel.org>