Just to let every one who is working with USB_BULK example, to know that there is no issue on the driver file that provided. It was a hardware issue on my side, USB0DM and USBID pins are connected.
Following command will work if you can't allowcate a pin to control feature (USB0EPEN to enbable the Vbus) then forcing the device with following
// // Set the USB stack mode to Device mode with VBUS monitoring. // USBStackModeSet(0, eUSBModeForceDevice, 0);
if you have implemented a hardware for USB0EPEN, USBID(PB0), USB_VBUS(PB1)