Refactor bootloader_jump() implementations (#15450)

* Refactor `bootloader_jump()` implementations

* Fix tests?

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

tmk_core/protocol/arm_atsam/startup.c

@@ -28,7 +28,6 @@
  */
 
 #include "samd51.h"
-#include "md_bootloader.h"
 
 /* Initialize segments */
 extern uint32_t _sfixed;
@@ -496,6 +495,11 @@ __attribute__((section(".vectors"))) const DeviceVectors exception_table = {
 #endif
 };
 
+// WARNING: These are only for CTRL bootloader release "v2.18Jun 22 2018 17:28:08" for bootloader_jump support
+extern uint32_t _eram;
+#define BOOTLOADER_MAGIC 0x3B9ACA00
+#define MAGIC_ADDR (uint32_t *)((intptr_t)(&_eram) - 4)
+
 /**
  * \brief This is the code that gets called on processor reset.
  * To initialize the device, and call the main() routine.