According to the bq27000 datasheet the current should be calculated by
the following formula:
    current = AI * 3570 / 20

This patch adjust the drivers code accordingly.
Signed-off-by: NPali Rohár <pali.rohar@gmail.com>
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Acked-by: NRodolfo Giometti <giometti@linux.it>
Tested-by: NGrazvydas Ignotas <notasas@gmail.com>