io_uring: kill dead REQ_F_LINK_DONE flag

We had no more use for this flag after the conversion to io-wq, kill it
off.

Fixes: 561fb04a ("io_uring: replace workqueue usage with io-wq")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -329,7 +329,6 @@ struct io_kiocb {
 #define REQ_F_IO_DRAIN		16	/* drain existing IO first */
 #define REQ_F_IO_DRAINED	32	/* drain done */
 #define REQ_F_LINK		64	/* linked sqes */
-#define REQ_F_LINK_DONE		128	/* linked sqes done */
 #define REQ_F_FAIL_LINK		256	/* fail rest of links */
 #define REQ_F_SHADOW_DRAIN	512	/* link-drain shadow req */
 #define REQ_F_TIMEOUT		1024	/* timeout request */
@@ -731,7 +730,6 @@ static void io_req_link_next(struct io_kiocb *req, struct io_kiocb **nxtptr)
 			nxt->flags |= REQ_F_LINK;
 		}
 
-		nxt->flags |= REQ_F_LINK_DONE;
 		/*
 		 * If we're in async work, we can continue processing the chain
 		 * in this context instead of having to queue up new async work.