regulator: fixed: Mark regulator-fixed-domain as deprecated

A power domain should not be modelled as a regulator, not even for the
simplest case as recent discussions have concluded around the existing
regulator-fixed-domain DT binding.

Fortunately, there is only one user of the binding that was recently added.
Therefore, let's mark the binding as deprecated to prevent it from being
further used.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20210705133441.11344-1-ulf.hansson@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/fixed-regulator.yaml

@@ -57,12 +57,14 @@ properties:
     maxItems: 1
 
   power-domains:
+    deprecated: true
     description:
       Power domain to use for enable control. This binding is only
       available if the compatible is chosen to regulator-fixed-domain.
     maxItems: 1
 
   required-opps:
+    deprecated: true
     description:
       Performance state to use for enable control. This binding is only
       available if the compatible is chosen to regulator-fixed-domain. The