bq27x00: Return -ENODEV for properties if the battery is not present

This patch changes get_property callback of the bq27x00 battery to return
-ENODEV for properties other then the PROP_PRESENT if the battery is not
present.
The power subsystem core expects a driver to behave that way.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Tested-by: Grazvydas Ignotas <notasas@gmail.com>