Use the longest filename instead of just using the long filename in M27

Firmware/cardreader.cpp

@@ -498,7 +498,7 @@ void CardReader::getStatus()
           SERIAL_PROTOCOLLNPGM("Print saved");
       }
       else {
-          SERIAL_PROTOCOLLN(longFilename);
+          SERIAL_PROTOCOLLN(LONGEST_FILENAME);
           SERIAL_PROTOCOLRPGM(_N("SD printing byte "));////MSG_SD_PRINTING_BYTE
           SERIAL_PROTOCOL(sdpos);
           SERIAL_PROTOCOL('/');