dt-bindings: power: supply: Add pm8916 LBC

Qualcomm Linear Battery Charger is a CC/CV charger block in PM8916 PMIC.
Document it's DT binding.

Signed-off-by: Nikita Travkin <nikita@trvn.ru>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230915-pm8916-bms-lbc-v3-2-f30881e951a0@trvn.ru
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>