blk-throttle: enable hierarchical throttle in cgroup v1

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4R7RE


CVE: NA

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blkio subsytem is not under default hierarchy in cgroup v1 by default,
which means configurations will only be effective on current cgroup
for io throttle.

This patch introduces a new feature that enable default hierarchy for
io throttle, which means configurations will be effective on child cgroups.
Such feature is disabled by default, and can be enabled by adding
"blkcg_global_limit=1" or "blkcg_global_limit=Y" or "blkcg_global_limit=y"
in boot cmd.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Tao Hou <houtao1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>