arm64: dts: qcom: sc7180: Add cmd_db reserved area

Command_db provides mapping for resource key and address managed
by remote processor. Add cmd_db reserved memory area.

Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20191108092824.9773-5-rnayak@codeaurora.org


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