dt-bindings: power: supply: axp20x: add AXP813 AC power DT binding

The AXP803/AXP813 AC power supply can limit input current and voltage.
Signed-off-by: Oskari Lemmela <oskari@lemmela.net>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Quentin Schulz <quentin.schulz@bootlin.com>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Tested-by: Vasily Khoruzhick <anarsoul@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Documentation/devicetree/bindings/power/supply/axp20x_ac_power.txt

@@ -4,6 +4,7 @@ Required Properties:
  - compatible: One of:
 			"x-powers,axp202-ac-power-supply"
 			"x-powers,axp221-ac-power-supply"
+			"x-powers,axp813-ac-power-supply"
 
 This node is a subnode of the axp20x PMIC.
 
@@ -13,6 +14,8 @@ reading ADC channels from the AXP20X ADC.
 The AXP22X is only able to tell if an AC power supply is present and
 usable.
 
+AXP813/AXP803 are able to limit current and supply voltage
+
 Example:
 
 &axp209 {