Refactor bootloader_jump() implementations (#15450)

* Refactor `bootloader_jump()` implementations

* Fix tests?

* Rename `atmel-samba` to `md-boot`

platforms/avr/bootloaders/bootloadhid.c

@@ -0,0 +1,34 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "bootloader.h"
+
+#include <avr/eeprom.h>
+#include <avr/wdt.h>
+
+__attribute__((weak))
+void bootloader_jump(void) {
+    // force bootloadHID to stay in bootloader mode, so that it waits
+    // for a new firmware to be flashed
+    // NOTE: this byte is part of QMK's "magic number" - changing it causes the EEPROM to be re-initialized
+    // thus every time the device is flashed the EEPROM will be wiped
+    eeprom_write_byte((uint8_t *)1, 0x00);
+
+    // watchdog reset
+    wdt_enable(WDTO_250MS);
+    for (;;)
+        ;
+}