power: supply: max17042_battery: Add support for the VOLT_MIN property

The info is there, so lets export it, like we already do for VOLT_MAX.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>