Fill in serial field for all HID controllers using hidapi

Controllers/SinowealthController/SinowealthController.cpp

@@ -39,6 +39,17 @@ unsigned int SinowealthController::GetLEDCount()
     return(led_count);
 }
 
+std::string SinowealthController::GetSerialString()
+{
+    wchar_t serial_string[128];
+    hid_get_serial_number_string(dev_report_id_4, serial_string, 128);
+
+    std::wstring return_wstring = serial_string;
+    std::string return_string(return_wstring.begin(), return_wstring.end());
+
+    return(return_string);
+}
+
 void SinowealthController::SetLEDColor
     (
     RGBColor* color_buf