dt-bindings: ufs: qcom: document SC8180X UFS

Document already upstreamed and used Qualcomm SC8180x UFS host
controller to fix dtbs_check warnings like:

  sc8180x-primus.dtb: ufshc@1d84000: compatible:0: 'qcom,sc8180x-ufshc' is not one of ['qcom,msm8994-ufshc', ... ]
  sc8180x-primus.dtb: ufshc@1d84000: Unevaluated properties are not allowed ('compatible' was unexpected)

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240326174632.209745-1-krzysztof.kozlowski@linaro.org


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