message: Add a coment on _sram_origin's usage in elf2tab
diff: @@ -92,6 +92,9 @@ SECTIONS {
  * https://riscv.org/wp-content/uploads/2015/01/riscv-calling.pdf
  */
  .stack (NOLOAD) : {
  + /* _sram_origin is used by elf2tab:
  + * https://github.com/tock/elf2tab/blob/master/src/main.rs#L301
  + */
  _sram_origin = .;
  KEEP(*(.stack_buffer))
  . = ALIGN(16);
  