regulator: dt-bindings: fixed-regulator: Add a preferred node name

Define "regulator-[0-9]v[0-9]" as the preferred node name for fixed
regulators. Other suffixes with names are also accepted. Combined,
these make up about half of the existing names in use.

For now this only serves as documentation as the schema still allows
anything to avoid lots of additional warnings for something low priority
to fix. Once a "no deprecated" mode is added to the tools, warnings can
be enabled selectively.

Signed-off-by: Rob Herring (Arm) <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

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

···
         - gpios
 
 properties:
+  $nodename:
+    anyOf:
+      - description: Preferred name is 'regulator-[0-9]v[0-9]'
+        pattern: '^regulator(-[0-9]+v[0-9]+|-[0-9a-z-]+)?$'
+      - description: Any name allowed
+        deprecated: true
+
   compatible:
     enum:
       - regulator-fixed