dt-bindings: power: domain-idle-state: Allow idle-state-name

Allow specifying a name for idle states, similar to CPU idle states
in cpu/idle-states.yaml

Signed-off-by: Konrad Dybcio <[e-mail]>
Acked-by: Krzysztof Kozlowski <[e-mail]>
Message-ID: <[e-mail]>
Signed-off-by: Ulf Hansson <[e-mail]>

Documentation/devicetree/bindings/power/domain-idle-state.yaml

···
           (i.e. idle states node with entry-method property is set to "psci")
           must specify this property.
 
+      idle-state-name:
+        $ref: /schemas/types.yaml#/definitions/string
+        description:
+          A string used as a descriptive name for the idle state.
+
     required:
       - compatible
       - entry-latency-us