linker: use lowercase _sram_origin

layout_generic.ld

diff --git a/layout_generic.ld b/layout_generic.ld
index 369b32a..dd101ab 100644
--- a/layout_generic.ld
+++ b/layout_generic.ld
@@ -88,14 +88,14 @@
     /* Application stack */
     .stack (NOLOAD) :
     {
-        /* elf2tab requires that the `_SRAM_ORIGIN` symbol be present to
+        /* elf2tab requires that the `_sram_origin` symbol be present to
          * mark the first address in the SRAM memory. Since ELF files do
          * not really need to specify this address as they only care about
          * loading into flash, we need to manually mark this address for
          * elf2tab. elf2tab will use it to add a fixed address header in the
          * TBF header if needed.
          */
-        _SRAM_ORIGIN = .;
+        _sram_origin = .;
 
         . = . + STACK_SIZE;