blk-mq: fix typo in comment

Spelling mistake (triple letters) in comment.
Detected with the help of Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Link: https://lore.kernel.org/r/20220521111145.81697-29-Julia.Lawall@inria.fr


Signed-off-by: Jens Axboe <axboe@kernel.dk>