dt-bindings: remoteproc: qcom,wcnss: Deprecate regulators for PDs

dt-bindings: remoteproc: qcom,wcnss: Deprecate regulators for PDs

So far we have been doing all proxy votes by voting for raw voltages/load
through the regulator interface. But actually VDDCX and VDDMX represent
power domains that should be preferably managed using corner votes
through the power domain interface.

Document that those should be specified as power domains for
qcom,pronto-v1/2-pil and deprecate using them through the regulator
interface.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20200916104135.25085-8-stephan@gerhold.net
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>