power: supply: max8998_charger: Correct ONLINE and add STATUS props

The ONLINE prop should be when the charger is present (ie able to
charge), however, it was for when it was actually charging or not.
Instead, add the STATUS prop to show whether charging is actually
going on or not.

The magic numbers have been ported from a downstream kernel for the
SGH-T959V.

Signed-off-by: Jonathan Bakker <xc-racer2@live.ca>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>