dt-bindings: mfd: 88pm886: Add #io-channel-cells

Add an #io-channel-cells property to the Marvell 88PM886 PMIC binding to
allow referencing the IO channels exposed by its GPADC.

Acked-by: Karel Balej <balejk@matfyz.cz> # for the PMIC
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Duje Mihanović <duje@dujemihanovic.xyz>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: LegoLivesMatter

Documentation/devicetree/bindings/mfd/marvell,88pm886-a1.yaml

@@ -35,6 +35,9 @@ properties:
         description: LDO or buck regulator.
         unevaluatedProperties: false
 
+  '#io-channel-cells':
+    const: 1
+
 required:
   - compatible
   - reg
@@ -53,6 +56,7 @@ examples:
         reg = <0x30>;
         interrupts = <0 4 IRQ_TYPE_LEVEL_HIGH>;
         interrupt-parent = <&gic>;
+        #io-channel-cells = <1>;
         wakeup-source;
 
         regulators {