dt-bindings: thermal: amlogic,thermal: add optional power-domains

On newer SoCs, the thermal hardware can require a power domain to
operate so add corresponding optional property.

Signed-off-by: George Stark <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Daniel Lezcano <[e-mail]>

Documentation/devicetree/bindings/thermal/amlogic,thermal.yaml

···
   clocks:
     maxItems: 1
 
+  power-domains:
+    maxItems: 1
+
   amlogic,ao-secure:
     description: phandle to the ao-secure syscon
     $ref: /schemas/types.yaml#/definitions/phandle