Thank you for your suggestion.

it's resolved my issue. I did update the function instead of updating the binding as there are some other values depend on "ddl.DataValueField = "Value";

In function I used value instead of description. now my function is:
function change() {
 if (document.getElementById("<%= ddlType.ClientID %>").value == "201") {
 document.getElementById("<%= fileUpload.ClientID %>").style.display = 'block'; 
 }
 else { document.getElementById("<%= fileUpload.ClientID %>").style.display = 'none';
 
 }
 }