power: supply: ab8500_fg: add missing destroy_workqueue in ab8500_fg_probe

In ab8500_fg_probe, misses destroy_workqueue in error path, this patch
fixes that.

Fixes: 010ddb81

 ("power: supply: ab8500_fg: Allocate wq in probe")
Signed-off-by: Gao Chao <gaochao49@huawei.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>