ublk: fix "immepdately" typo in comment

Looks like "immediately" was intended.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250430225234.2676781-3-csander@purestorage.com


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