There are two charger current limit registers:

- Fast charge current limit (which controls current going from the
  charger to the battery);
- CHGIN input current limit (which controls current going into the
  charger through the cable).

Add the necessary functions to retrieve the CHGIN input limit (from CHARGER
regulator) and maximum fast charge current values, and expose them as power
supply properties.
Tested-by: Henrik Grimler <henrik@grimler.se>
Signed-off-by: Artur Weber <aweber.kernel@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240816-max77693-charger-extcon-v4-3-050a0a9bfea0@gmail.comSigned-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>