Fix sysfs_root assignment with multiple identical devices

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index 6b70805..1a31892 100644
--- a/fio.h
+++ b/fio.h
@@ -647,6 +647,7 @@
 	struct list_head list;
 
 	char *name;
+	char *sysfs_root;
 	char path[256];
 	int major, minor;