blk-mq: remove unneeded needs_restart check

If code reaches here, needs_restart must be true. Remove this unneeded
needs_restart check. No functional change intended.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Link: https://lore.kernel.org/r/20220905101950.4606-1-linmiaohe@huawei.com


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