drivers: soc: qcom: rpmpd: Add msm8994 RPM Power Domains

MSM8994 uses similar to MSM8996, legacy-style voltage
control, but does not include a VDD_SC_CX line.

This setup is also correct for MSM8992.

Do note that there exist some boards that use a tertiary PMIC
(most likely pm8004), where SMPB on VDDGFX becomes SMPC. I
cannot test this configuration though.

Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Link: https://lore.kernel.org/r/20210118161943.105733-1-konrad.dybcio@somainline.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>