power: supply: axp288_charger: Simplify extcon cable handling

Simplify extcon cable handling using the new
devm_extcon_register_notifier_all function to listen to all cables
in one go.

Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>