The SDM670 uses RPMh for managing the PM660 and PM660L. Document RPMh
support for the PMIC.

Link: https://android.googlesource.com/kernel/msm/+/58064f13c0a436a82c35f2e3b5a122d874ae5846%5E%21/#F0Signed-off-by: Richard Acayan <mailingradian@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220920223331.150635-2-mailingradian@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>