just fix i

$file_name = underscore($_FILES['linkmanulas']['name']);
$file_name = round(microtime(true)) .''. $file_name;
$config = array(
'upload_path' => "./uploads/",
'allowed_types' => "gif|jpg|jpeg|png|iso|dmg|zip|rar|doc|docx|xls|xlsx|ppt|pptx|csv|ods|odt|odp|pdf|rtf|sxc|sxi|txt|exe|avi|mpeg|mp3|mp4|3gp",
'overwrite' => TRUE,
'max_size' => "2048000", // Can be set to particular file size , here it is 2 MB(2048 Kb)
'max_height' => "0",
'max_width' => "0",
'file_name' => $file_name
);

//$this->load->library('upload', $config);
if($this->upload->do_upload($file_name))
{
$data = array('upload_data' => $this->upload->data());
//return ;
print_r($data);
exit;
$this->load->view('admin/vwAddContent',$data);
}
else
{
$error = array('error' => $this->upload->display_errors());
print_r($error);
exit;
$this->load->view('admin/vwAddContent', $error);
}