Document "qcom,sm8250-ufshc" and "qcom,sm8350-ufshc" compatible string.
Use of "qcom,sm8250-ufshc" is already present upstream, so add misiing
documentation. "qcom,sm8350-ufshc" is for UFS HC found in SM8350 SoC.

Link: https://lore.kernel.org/r/20210204165234.61939-1-vkoul@kernel.orgReviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>