Add tcflush back into flush routine

https://github.com/Hamlib/Hamlib/issues/1241

src/serial.c

@@ -793,8 +793,8 @@ int HAMLIB_API serial_flush(hamlib_port_t *p)
     while (len > 0);
 
     p->timeout = timeout_save;
-    //rig_debug(RIG_DEBUG_VERBOSE, "tcflush%s\n", "");
-    //tcflush(p->fd, TCIFLUSH);
+    rig_debug(RIG_DEBUG_VERBOSE, "tcflush%s\n", "");
+    tcflush(p->fd, TCIFLUSH); // we also do this flush https://github.com/Hamlib/Hamlib/issues/1241
     return (RIG_OK);
 }