t/dedupe: use fio abstracted OS_O_DIRECT

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/t/dedupe.c b/t/dedupe.c
index 7edb3d8..030b4fc 100644
--- a/t/dedupe.c
+++ b/t/dedupe.c
@@ -431,7 +431,7 @@
 
 	flags = O_RDONLY;
 	if (odirect)
-		flags |= O_DIRECT;
+		flags |= OS_O_DIRECT;
 
 	memset(&file, 0, sizeof(file));
 	file.file_name = strdup(filename);