power: supply: ab8500: Remove flush_scheduled_work() call.

It seems to me that ab8500 driver is using dedicated workqueues and
is not calling schedule{,_delayed}_work{,_on}(). Then, there will be
no work to flush using flush_scheduled_work().

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>