io_uring: fill extra big cqe fields from req

The only user of io_req_complete32()-like functions is cmd
requests. Instead of keeping the whole complete32 family, remove them
and provide the extras in already added for inline completions
req->extra{1,2}. When fill_cqe_res() finds CQE32 option enabled
it'll use those fields to fill a 32B cqe.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/af1319eb661b1f9a0abceb51cbbf72b8002e019d.1655287457.git.asml.silence@gmail.com


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