io_uring: fix ->extra{1,2} misuse

We don't really know the state of req->extra{1,2] fields in
__io_fill_cqe_req(), if an opcode handler is not aware of CQE32 option,
it never sets them up properly. Track the state of those fields with a
request flag.

Fixes: 76c68fbf ("io_uring: enable CQE32")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/4b3e5be512fbf4debec7270fd485b8a3b014d464.1655287457.git.asml.silence@gmail.com


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