Split off diskutil include

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/stat.c b/stat.c
index a42ed98..44edd1e 100644
--- a/stat.c
+++ b/stat.c
@@ -8,6 +8,7 @@
 #include <math.h>
 
 #include "fio.h"
+#include "diskutil.h"
 
 /*
  * Cheesy number->string conversion, complete with carry rounding error.