Fix an off-by-one with --skip parameter

The default value of 0 is skipping the first frame.

src/bin/rav1e.rs

@@ -144,11 +144,9 @@ fn main() {
   );
 
   ctx.set_limit(cli.limit as u64);
-  let mut frame_current_count = 0;
 
-  while frame_current_count <= cli.skip {
-       y4m_dec.read_frame().expect("Skipped more frames than in the input");
-       frame_current_count+=1;
+  for _ in 0..cli.skip {
+    y4m_dec.read_frame().expect("Skipped more frames than in the input");
   }
 
   while let Ok(frame_info) = process_frame(&mut ctx, &mut cli.io.output, &mut y4m_dec, y4m_enc.as_mut()) {