dt-bindings: power: supply: Document Maxim MAX8971 charger

Add bindings for Maxim MAX8971 charger.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250430055114.11469-2-clamor95@gmail.com


Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>