io_uring: support to inject result for NOP

Support to inject result for NOP so that we can inject failure from
userspace. It is very helpful for covering failure handling code in
io_uring core change.

With nop flags, it becomes possible to add more test features on NOP in
future.

Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20240510035031.78874-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring: fail NOP if non-zero op flags is passed in

The NOP op flags should have been checked from beginning like any other
opcode, otherwise NOP may not be extended with the op flags.

Given both liburing and Rust io-uring crate always zeros SQE op flags, just
ignore users which play raw NOP uring interface without zeroing SQE, because
NOP is just for test purpose. Then we can save one NOP2 opcode.

Suggested-by: Jens Axboe <axboe@kernel.dk>
Fixes: 2b188cc1bb85 ("Add io_uring IO interface")
Cc: stable@vger.kernel.org
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20240510035031.78874-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring: kill extra io_uring_types.h includes

io_uring/io_uring.h already includes io_uring_types.h, no need to
include it every time. Kill it in a bunch of places, it prepares us for
following patches.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/94d8c943fbe0ef949981c508ddcee7fc1c18850f.1655384063.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring: move nop into its own file

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