atsamd: Use local linker script

Use a local linker script instead of the linker script provided by
Atmel.  This will allow Klipper to use dynamic memory allocation.

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

src/atsamd/samd.lds.S

@@ -0,0 +1,63 @@
+/* Linker script for atsamd chips
+ *
+ * Copyright (C) 2019  Kevin O'Connor <kevin@koconnor.net>
+ *
+ * This file may be distributed under the terms of the GNU GPLv3 license.
+ */
+
+#include "autoconf.h"
+
+OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
+OUTPUT_ARCH(arm)
+
+MEMORY
+{
+  rom (rx) : ORIGIN = CONFIG_FLASH_START , LENGTH = CONFIG_FLASH_SIZE
+  ram (rwx) : ORIGIN = 0x20000000, LENGTH = CONFIG_RAM_SIZE
+}
+
+SECTIONS
+{
+    .text : {
+        . = ALIGN(4);
+        _sfixed = .;
+        KEEP(*(.vectors .vectors.*))
+        *(.text .text.*)
+        *(.rodata .rodata*)
+
+        . = ALIGN(4);
+        KEEP(*(.init))
+        . = ALIGN(4);
+        KEEP(*(.fini))
+    } > rom
+
+    . = ALIGN(4);
+    _etext = .;
+
+    .relocate : AT (_etext)
+    {
+        . = ALIGN(4);
+        _srelocate = .;
+        *(.ramfunc .ramfunc.*);
+        *(.data .data.*);
+        . = ALIGN(4);
+        _erelocate = .;
+    } > ram
+
+    .bss (NOLOAD) :
+    {
+        . = ALIGN(4);
+        _szero = .;
+        *(.bss .bss.*)
+        *(COMMON)
+        . = ALIGN(4);
+        _ezero = .;
+    } > ram
+
+    _sstack = 0x20000000 + CONFIG_RAM_SIZE - CONFIG_STACK_SIZE ;
+    .stack _sstack (NOLOAD) :
+    {
+        . = . + CONFIG_STACK_SIZE;
+        _estack = .;
+    } > ram
+}