power: supply: max8997_charger: Set CHARGER current limit

Register for extcon notification and set charging current depending on
the detected cable type. Current values are taken from vendor kernel,
where most charger types end up setting 650mA [0].

Also enable and disable the CHARGER regulator based on extcon events.

[0] https://github.com/krzk/linux-vendor-backup/blob/samsung/galaxy-s2-epic-4g-touch-sph-d710-exynos4210-dump/drivers/misc/max8997-muic.c#L1675-L1678



Signed-off-by: Timon Baetz <timon.baetz@protonmail.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>