Updater: Write functional ram code loader

Updater RAM Code
----------------
* Ack running watchdog every 250 ms
* Blink green LED every 250 ms

Firmware
--------
* Add RAM code loader
* Reorganize initialization
* Add update command to shell

stm-firmware/include/reflow-controller/updater/updater.h

@@ -0,0 +1,31 @@
+/* Reflow Oven Controller
+*
+* Copyright (C) 2020  Mario Hüttel <mario.huettel@gmx.net>
+*
+* This file is part of the Reflow Oven Controller Project.
+*
+* The reflow oven controller is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License version 2 as
+* published by the Free Software Foundation.
+*
+* The Reflow Oven Control Firmware is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with the reflow oven controller project.
+* If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __UPDATER_UPDATER_H__
+#define __UPDATER_UPDATER_H__
+
+#define UPDATER_RAM_CODE_BASE_ADDRESS (0x20000000UL)
+
+/**
+ * @brief Start the RAM Code of the updater. This function will never return!
+ */
+void __attribute__((noreturn)) start_updater(void);
+
+#endif /* __UPDATER_UPDATER_H__ */