io_uring: don't forget cflags in io_recv()

Instead of returning error from io_recv(), go through generic cleanup
path, because it'll retain cflags for userspace. Do the same for
io_send() for consistency.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>