2.5.3 Configuring the Library
The application designer must specify the following configuration parameters while using
            the CDC Function Driver. The configuration macros that implement these parameters must
            be located in the system_config.h file in the application project and a
            compiler include path (to point to the folder that contains this file) should be
            specified.
Macros
| Name | Description | 
| USB_DEVICE_CDC_INSTANCES_NUMBER | Specifies the number of CDC instances. | 
| USB_DEVICE_CDC_QUEUE_DEPTH_COMBINED | Specifies the combined queue size of all CDC instances. | 
| Configuration on MCC | This section describes the symbols available in the MCC that can be configured. | 
