power: supply: ab8500_fg: Drop useless parameter

All calls to ab8500_fg_calc_cap_discharge_voltage() require
compensation and pass true as the second argument so just drop
this argument.

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