power: supply: max8997_charger: Switch to new binding

Get regulator from parent device's node and extcon by name.

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>