soc: qcom: rpmpd: Add MSM8916 power domains

MSM8916 has two RPM power domains: VDDCX and VDDMX.
Add the necessary definitions to manage them with rpmpd.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20200916104135.25085-4-stephan@gerhold.net


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