arm64: dts: qcom: sc7180: Add xo clock for eMMC and Sd card

The calculations for the DLL register values are based on the clock rate
of the reference clock. Provide the reference clock in the definition of
the two SDHCI controllers to not rely on the default values.

Reviewed-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Signed-off-by: Shaik Sajida Bhanu <sbhanu@codeaurora.org>
Link: https://lore.kernel.org/r/1623309107-27833-1-git-send-email-sbhanu@codeaurora.org


[bjorn: Rewrote commit message]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>