io_uring: missed req_init_async() for IOSQE_ASYNC

IOSQE_ASYNC branch of io_queue_sqe() is another place where an
unitialised req->work can be accessed (i.e. prior io_req_init_async()).
Nothing really bad though, it just looses IO_WQ_WORK_CONCURRENT flag.

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

fs/io_uring.c

@@ -5730,6 +5730,7 @@ fail_req:
 		 * Never try inline submit of IOSQE_ASYNC is set, go straight
 		 * to async execution.
 		 */
+		io_req_init_async(req);
 		req->work.flags |= IO_WQ_WORK_CONCURRENT;
 		io_queue_async_work(req);
 	} else {