power: supply: bq27xxx: Add cache parameter to bq27xxx_battery_current_and_status()

Add a cache parameter to bq27xxx_battery_current_and_status() so that
it can optionally use cached flags instead of re-reading them itself.

This is a preparation patch for making bq27xxx_battery_update() check
the status and have it call power_supply_changed() on status changes.

Fixes: 297a533b

 ("bq27x00: Cache battery registers")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>