power: supply: max17042: extend help/description

Reorganize the Kconfig driver description and mention all supported
models.  This helps when choosing drivers for given system.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>