block: don't ignore REQ_NOWAIT for direct IO

mainline inclusion
from mainline-v5.12-rc6
commit f8b78caf
category: bugfix
bugzilla: 186136, https://gitee.com/openeuler/kernel/issues/I4RM1D


CVE: NA

-------------------------------------------------

If IOCB_NOWAIT is set on submission, then that needs to get propagated to
REQ_NOWAIT on the block side. Otherwise we completely lose this
information, and any issuer of IOCB_NOWAIT IO will potentially end up
blocking on eg request allocation on the storage side.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
conflict:
        fs/block_dev.c
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>