arm: boot: dts: qcom-msm8974: Sort and clean up nodes

Notable changes:
- cpu-pmu{} -> pmu {}
- removed regulators from modem; these should be set per-board
- removed model=""; this gets overwritten anyway
- tcsr-mutex is now brought out of soc{}

Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>