Fix issues for NTAG21x tags

- Change default tag from NTAG_213 to NTAG_UNKNOWN so unknown tags can
  be detected.  ntag_get_info() MUST be called after connect;
- Fix reuse function which used to reset all tag info;
- Introduce ntag21x error reporting through freefare_error(3);

examples/mifare-desfire-ev1-configure-random-uid.c

@@ -153,8 +153,8 @@ main(int argc, char *argv[])
 		    }
 		}
 		break;
-	    case 4: // Random UID
-	    {} // Compilation fails if label is directly followed by the declaration rather than a statement
+	    case 4: { // Random UID
+	    } // Compilation fails if label is directly followed by the declaration rather than a statement
 	    MifareDESFireKey key_picc = mifare_desfire_des_key_new_with_version(key_data_picc);
 	    res = mifare_desfire_authenticate(tags[i], 0, key_picc);
 	    if (res < 0) {