arm64: dts: qcom: sdm845: Add SD nodes for sdm845-mtp

Enable support for one of the micro SD slots on the MTP.

Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Evan Green <evgreen@chromium.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>