Split off diskutil include

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/ioengines.c b/ioengines.c
index 7840d2a..51cf1ba 100644
--- a/ioengines.c
+++ b/ioengines.c
@@ -17,6 +17,7 @@
 #include <assert.h>
 
 #include "fio.h"
+#include "diskutil.h"
 
 static FLIST_HEAD(engine_list);