message: rafs: use real root ino when perform dynamic prefetch
diff: @@ -553,15 +553,16 @@ impl RafsSuper {
  /// Convert a file path to an inode number.
  pub fn ino_from_path(&self, f: &Path) -> Result<u64> {
  + let root_ino = self.superblock.root_ino();
  if f == Path::new("/") {
  - return Ok(ROOT_ID);
  + return Ok(root_ino);
  }
  if !f.starts_with("/") {
  return Err(einval!());
  }
  - let mut parent = self.get_inode(ROOT_ID, self.validate_digest)?;
  + let mut parent = self.get_inode(root_ino, self.validate_digest)?;
  let entries = f
  .components()
  