io_uring: remove redundant variable pointer nxt and io_wq_assign_next call

An earlier commit "io_uring: remove @nxt from handlers" removed the
setting of pointer nxt and now it is always null, hence the non-null
check and call to io_wq_assign_next is redundant and can be removed.

Addresses-Coverity: ("'Constant' variable guard")
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -3509,14 +3509,11 @@ static void __io_sync_file_range(struct io_kiocb *req)
 static void io_sync_file_range_finish(struct io_wq_work **workptr)
 {
 	struct io_kiocb *req = container_of(*workptr, struct io_kiocb, work);
-	struct io_kiocb *nxt = NULL;
 
 	if (io_req_cancelled(req))
 		return;
 	__io_sync_file_range(req);
 	io_put_req(req); /* put submission ref */
-	if (nxt)
-		io_wq_assign_next(workptr, nxt);
 }
 
 static int io_sync_file_range(struct io_kiocb *req, bool force_nonblock)