block: remove unnecessary trailing '\'

While harmless, the blank line is certainly not intended to be part of
the rq_list_for_each() macro. Remove it.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20211222215239.1768164-1-kbusch@kernel.org


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