sched: Add frequency control for load update in scheduler_tick

hulk inclusion
category: feature
bugzilla: 175551 https://gitee.com/openeuler/kernel/issues/I4DVI3



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Avaliable for control thread load update frequency manually,
by echo 10~30 > /proc/sys/kernel/sched_tick_update_load.
Available for switch on/off update thread load in scheduler_tick.

Signed-off-by: Yu Jiahua <yujiahua1@huawei.com>
Reviewed-by: Chen Hui <judy.chenhui@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>