Bugfix/zephyr build for minimal ram (#606)

* Removed BACnet objects from ports/zephyr. There should only be datalink and OS related interfaces in OS ports.

* Added Kconfig and bacnet-config.h options in ports/zephyr to keep small footprint for MCUs having less RAM

* Changed ports/zephry for BACnet/IP and date-time with latest zephyr OS

src/bacnet/config.h

@@ -1,27 +1,14 @@
-/**************************************************************************
-*
-* Copyright (C) 2004 Steve Karg <skarg@users.sourceforge.net>
-*
-* Permission is hereby granted, free of charge, to any person obtaining
-* a copy of this software and associated documentation files (the
-* "Software"), to deal in the Software without restriction, including
-* without limitation the rights to use, copy, modify, merge, publish,
-* distribute, sublicense, and/or sell copies of the Software, and to
-* permit persons to whom the Software is furnished to do so, subject to
-* the following conditions:
-*
-* The above copyright notice and this permission notice shall be included
-* in all copies or substantial portions of the Software.
-*
-* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
-* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
-* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
-* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
-* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-*
-*********************************************************************/
+/**
+ * @file
+ * @brief Default configuration for BACnet Stack library
+ * @author Steve Karg <skarg@users.sourceforge.net>
+ * @date 2004
+ * @section LICENSE
+ * 
+ * Copyright (C) 2004 Steve Karg <skarg@users.sourceforge.net>
+ * 
+ * SPDX-License-Identifier: MIT
+ */
 #ifndef CONFIG_H
 #define CONFIG_H