atsamd: Update code to use armcm_boot mechanism

Replace the custom linker scripts with the src/generic/armcm_boot.c
mechanism.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/atsamd/main.c

@@ -4,28 +4,12 @@
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
-#include "command.h" // DECL_CONSTANT
+#include "command.h" // DECL_CONSTANT_STR
 #include "internal.h" // NVIC_SystemReset
 #include "sched.h" // sched_main
 
 DECL_CONSTANT_STR("MCU", CONFIG_MCU);
 
-// Return the start of memory available for dynamic allocations
-void *
-dynmem_start(void)
-{
-    extern uint32_t _ezero;
-    return &_ezero;
-}
-
-// Return the end of memory available for dynamic allocations
-void *
-dynmem_end(void)
-{
-    extern uint32_t _sstack;
-    return &_sstack;
-}
-
 void
 command_reset(uint32_t *args)
 {
@@ -37,7 +21,6 @@ DECL_COMMAND_FLAGS(command_reset, HF_IN_SHUTDOWN, "reset");
 int
 main(void)
 {
-    SystemInit();
     sched_main();
     return 0;
 }