blk-cgroup: fix missing pd_online_fn() while activating policy

stable inclusion
from stable-v5.10.167
commit 19c9a2ba46996f2dbc5bfbf1e8f3dc50b347c91c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7TH9O

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=19c9a2ba46996f2dbc5bfbf1e8f3dc50b347c91c



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[ Upstream commit e3ff8887 ]

If the policy defines pd_online_fn(), it should be called after
pd_init_fn(), like blkg_create().

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230103112833.2013432-1-yukuai1@huaweicloud.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>