arm64: dts: qcom: rb5: Add support for uSD card

Add support for uSD card on RB5 using the SDHC2 interface.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
[DB: disabled 1.8V support to get SDHC to work]
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20201028190955.1264526-2-dmitry.baryshkov@linaro.org


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>