fixed PPU scroll issue

src/main.rs

@@ -79,7 +79,7 @@ fn run_dbg(path: &str) {
     cpu.reset(&mut bus);
     let mut dumper = dump::Dumper::new();
     let mut renderer = PpmRenderer::new();          // <-- add this
-    let frames: u32 = 360;
+    let frames: u32 = 1800;
 
     for f in 0..frames {
         while !bus.frame_done() {