power: supply: ab8500: Standardize CC current

The current used in the constant current phase of the charging
exist in struct power_supply_battery_info as
constant_charge_current_max_ua.

Switch the custom property max_out_curr to this and
consequentally change everything that relates to this value
over to using microamperes rather than milliamperes so
we align internal representation of current with the
power core. Prefix every variable we change with *_ua
to indicate the unit everywhere but also to make sure
we do not miss any outlier.

Drop some duplicate unused defines in a header.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>