Add missing switch case

Fix build issue:

```
/tmp/libfreefare/libfreefare/freefare.c:172:13: error: enumeration value 'NMT_BARCODE' not handled in switch
      [-Werror,-Wswitch]
    switch (tag->info.nm.nmt) {
            ^
1 error generated.
```

libfreefare/freefare.c

@@ -188,6 +188,7 @@ freefare_get_tag_uid(FreefareTag tag)
  case NMT_ISO14443B:
  case NMT_ISO14443BI:
  case NMT_JEWEL:
+ case NMT_BARCODE:
  res = strdup("UNKNOWN");
  }
  return res;