power: supply: bq27xxx: Use mod_delayed_work() instead of cancel() + schedule()

Use mod_delayed_work() instead of separate cancel_delayed_work_sync() +
schedule_delayed_work() calls.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>