arm64: dts: qcom: msm8992: Add PSCI support.

This SoC's firmware does not fully support the PSCI
spec, but it's good enough to bring the cores up.

Signed-off-by: Konrad Dybcio <konradybcio@gmail.com>
Link: https://lore.kernel.org/r/20200625182118.131476-11-konradybcio@gmail.com


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