sched: fix smart grid usage count

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7D98G


CVE: NA

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smart_grid_usage_dec() should called when free taskgroup
if the mode is auto.

Signed-off-by: Hui Tang <tanghui20@huawei.com>
Reviewed-by: Zhang Qiao <zhangqiao22@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>