Added cleanup of vairables at unmap

Signed-off-by: Lenard Nagy <lenard.nagy@ericsson.com>
diff --git a/src/SerialPort.cc b/src/SerialPort.cc
index d5be612..7978fc7 100644
--- a/src/SerialPort.cc
+++ b/src/SerialPort.cc
@@ -180,6 +180,8 @@
   {
     Handler_Remove_Fd_Read(device_fd);
     close(device_fd);
+    free(param_device_file);
+    ret_buffer.clean_up();
   }
 
   void SerialPort::user_start()