dt-bindings: soc: qcom: qcom,saw2: define optional regulator node

The SAW2 device can optionally provide a voltage regulator supplying the
CPU core, cluster or L2 cache. Change the boolean 'regulator' property
into a proper regulator description. This breaks schema compatibility
for the sake of properly describing the regulator.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20240102-saw2-spm-regulator-v7-3-0472ec237f49@linaro.org


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