Hello Soumya,
what u can do is, before calling file upload service do a get call to the same service and get the X-CSRF token and use the same token for calling file upload service.
For Ex.
var headers = {
"X-Requested-With": "XMLHttpRequest",
"Content-Type": "application/atom+xml",
"X-CSRF-Token":"Fetch"
};
var oModel = new sap.ui.model.odata.ODataModel("XXXXXX", "false", "", "",headers, true);
sap.ui.getCore().setModel(oModel, "XCRFTokenModel");
sap.ui.getCore().getModel("XCRFTokenModel").refreshSecurityToken();
var rowSelObj = sap.ui.getCore().getModel("rowSelObj");
if (fileName !== null && fileName !== "") {
oFileUploaderDocTab.insertHeaderParameter(new sap.ui.unified.FileUploaderParameter({name: "x-csrf-token", value: sap.ui.getCore().getModel("XCRFTokenModel").getHeaders()["x-csrf-token"]}));
It should solve your problem 
