blk-cgroup: Fix typo in comment

Replace assocating with associating.
Replace intiailized with initialized.

Signed-off-by: Kemeng Shi <shikemeng@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20221206093307.378249-1-shikemeng@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>