dt-bindings: power: rpmpd: Add MSM8917, MSM8937 and QM215

dt-bindings: power: rpmpd: Add MSM8917, MSM8937 and QM215

The MSM8917, MSM8937 and QM215 SoCs have VDDCX and VDDMX power domains
controlled in voltage level mode. Define the MSM8937 and QM215 power
domains as aliases because these SoCs are similar to MSM8917 and may
share some parts of the device tree.

Also add the compatibles for these SoCs to the documentation, with
qcom,msm8937-rpmpd using qcom,msm8917-rpmpd as a fallback compatible
because there are no known differences. QM215 is not compatible with
these because it uses different regulators.

Signed-off-by: Otto Pflüger <otto.pflueger@abscue.de>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231014133823.14088-2-otto.pflueger@abscue.de
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>