soc: qcom: spm: add support for voltage regulator

The SPM / SAW2 device also provides a voltage regulator functionality
with optional AVS (Adaptive Voltage Scaling) support. The exact register
sequence and voltage ranges differs from device to device.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Acked-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20240102-saw2-spm-regulator-v7-5-0472ec237f49@linaro.org


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