During probe, it makes no sense to take care to first not issue any
i2c commands to verify if the connected part really is a bq24735, to
later simply fail the probe in the next step when trying to configure
the charger. So, delay configuration of the charging parameters until
the charger is accessible (i.e. when the AC adapter is present) as
part of enabling the charging.

This also fixes the rather serious issue that the charging parameters
are lost when the AC adapter is disconnected.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Sebastian Reichel <sre@kernel.org>