Apply __force cast to restricted io_req_flags_t type to fix
the following sparse warning:

io_uring/io_uring.c:2026:23: sparse: warning: cast to restricted io_req_flags_t

No functional changes intended.
Signed-off-by: Min-Hua Chen <minhuadotchen@gmail.com>
Link: https://lore.kernel.org/r/20240922104132.157055-1-minhuadotchen@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>