list_ports: add USB location string, shorter descriptions, CDC/ACM fix
list_ports: add USB location string, shorter descriptions, CDC/ACM fix

- the location is in the form <bus>'-'<port>'.'<port>...
- use the product string only to make descriptions shorted (separate
  long description function available). for CDC/ACM use the interface string
  when not empty.
- fix usb/usb-serial check
DavidHowlett/pyserial-1,hoihu/pyserial