drop global symbol and replace with board.iserial

Author: facchinm

arduino-core/src/cc/arduino/packages/discoverers/serial/SerialBoardsLister.java

@@ -86,6 +86,7 @@ public void run() {
       if (boardData != null) {
         boardPort.getPrefs().put("vid", boardData.get("vid").toString());
         boardPort.getPrefs().put("pid", boardData.get("pid").toString());
+        boardPort.getPrefs().put("iserial", boardData.get("iserial").toString());
 
         TargetBoard board = (TargetBoard) boardData.get("board");
         if (board != null) {

arduino-core/src/processing/app/Platform.java

@@ -167,7 +167,6 @@ protected Map<String, Object> resolveDeviceByVendorIdProductId(Map<String, Targe
                 boardData.put("vid", vids.get(i));
                 boardData.put("pid", pids.get(i));
                 boardData.put("iserial", readVIDPID.substring(vidPid.length()));
-                PreferencesData.set("serial.port.iserial", readVIDPID.substring(vidPid.length()+1));
                 return boardData;
               }
             }