arm64: dts: qcom: x1e80100: Add missing system-wide PSCI power domain

arm64: dts: qcom: x1e80100: Add missing system-wide PSCI power domain

Previous Qualcomm SoCs over the past couple years have used the Arm DSU
architecture, which basically unified the meaning of the "cluster" and
"system". This is however clearly not the case on X1E, as can be seen
by three separate cluster power domains.

Add the lacking system-level power domain. For now it's going to be
always-on, as no system-wide idle states are defined at the moment.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20240102-topic-x1e_fixes-v1-3-70723e08d5f6@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>