ARM: dts: qcom: msm8974: Start using rpmpd for power domains

ARM: dts: qcom: msm8974: Start using rpmpd for power domains

Due to historical reasons all msm8974 boards have used the CX power rail
as regulator instead of going through the power domain framework.

Since rpmpd has gained msm8974 support quite a bit ago, let's start
using it and replace all usages of pm8841_s2 (CX), pm8841_s4 (GFX) and
for the boards using pma8084 pma8084_s2 (CX), pma8084_s7 (GFX).

For reference, downstream is using GFX power rail as parent-supply for
mmcc's OXILI_GDSC GDSC which then is used for GPU, but nothing there is
modelled upstream.

Signed-off-by: Luca Weiss <luca@lucaweiss.eu>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250621-msm8974-rpmpd-switch-v1-4-0a2cb303c446@lucaweiss.eu
Signed-off-by: Bjorn Andersson <andersson@kernel.org>