overlay: Distinguish the root debugfs path and our dri node

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/overlay/debugfs.h b/overlay/debugfs.h
index 0e5ad95..8a1c60a 100644
--- a/overlay/debugfs.h
+++ b/overlay/debugfs.h
@@ -26,6 +26,8 @@
 #define DEBUGFS_H
 
 extern char debugfs_path[128];
+extern char debugfs_dri_path[128];
+
 int debugfs_init(void);
 
 #endif /* DEBUGFS_H */