power_supply: bq27x00: add status and time properties

The BQ27x00 series of chips can report time-to-empty and
time-to-full, so let's add corresponding properties.
Also report charge status based on status flag register.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>