dt-bindings: power: supply: gpio-charger: add support for default charge current limit

With DT properties charge-current-limit-gpios and
charge-current-limit-mapping one can define charge current limits in uA
using up to 32 GPIOs. Add property charge-current-limit-default-microamp
which selects a default charge current limit that must be listed in
charge-current-limit-mapping.
This is helpful when the smallest possible charge current limit is 0uA. The
driver defaults to the smallest possible value at the moment, which
disables charging on probe. With the default its possible to setup a safe
charge current limit.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
Link: https://lore.kernel.org/r/20241218-default-charge-current-limit-v3-1-b26118cf06b5@liebherr.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Documentation/devicetree/bindings/power/supply/gpio-charger.yaml

@@ -58,6 +58,10 @@ properties:
             charge-current-limit-gpios property. Bit 1 second to last
             GPIO and so on.
 
+  charge-current-limit-default-microamp:
+    description: Default charge current limit. Must be listed in
+      charge-current-limit-mapping.
+
 required:
   - compatible
 
@@ -72,6 +76,7 @@ anyOf:
 dependencies:
   charge-current-limit-gpios: [ charge-current-limit-mapping ]
   charge-current-limit-mapping: [ charge-current-limit-gpios ]
+  charge-current-limit-default-microamp: [charge-current-limit-mapping]
 
 additionalProperties: false
 
@@ -91,4 +96,5 @@ examples:
       charge-current-limit-mapping = <2500000 0x00>, // 2.5 A => both GPIOs low
                                      <700000 0x01>, // 700 mA => GPIO A.12 high
                                      <0 0x02>; // 0 mA => GPIO A.11 high
+      charge-current-limit-default-microamp = <700000>;
     };