usb_enable() must be called by the application.
The application may want to register usb_dc_status_callback
and trace usb status codes (usb_dc_status_code).
Signed-off-by: Emil Obalski <emil.obalski@nordicsemi.no>
This is more a sample than a test, so put it under samples with the goal
of having dedicated tracing tests in the future under tests.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>