io_uring: io_async_buf_func() need not test page bit

Since we don't do exclusive waits or wakeups, we know that the bit is
always going to be set. Kill the test. Also see commit:

2a9127f ("mm: rewrite wait_on_page_bit_common() logic")

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

fs/io_uring.c

@@ -2965,10 +2965,6 @@ static int io_async_buf_func(struct wait_queue_entry *wait, unsigned mode,
 	if (!wake_page_match(wpq, key))
 		return 0;
 
-	/* Stop waking things up if the page is locked again */
-	if (test_bit(key->bit_nr, &key->page->flags))
-		return -1;
-
 	list_del_init(&wait->entry);
 
 	init_task_work(&req->task_work, io_req_task_submit);