boardloader: move memset_reg to separate source file

SConscript.boardloader

@@ -71,6 +71,7 @@ SOURCE_STMHAL = [
 
 SOURCE_BOARDLOADER = [
     'embed/common/vectortable.s',
+    'embed/common/util.s',
     'embed/boardloader/startup.s',
     'embed/boardloader/main.c',
 ]

embed/boardloader/startup.s

@@ -2,20 +2,6 @@
 
   .text
 
-  .global memset_reg
-  .type memset_reg, STT_FUNC
-memset_reg:
-  // call with the following (note that the arguments are not validated prior to use):
-  // r0 - address of first word to write (inclusive)
-  // r1 - address of first word following the address in r0 to NOT write (exclusive)
-  // r2 - word value to be written
-  // both addresses in r0 and r1 needs to be divisible by 4!
-  .L_loop_begin:
-    str r2, [r0], 4 // store the word in r2 to the address in r0, post-indexed
-    cmp r0, r1
-  bne .L_loop_begin
-  bx lr
-
   .global reset_handler
   .type reset_handler, STT_FUNC
 reset_handler:

embed/common/util.s

@@ -0,0 +1,19 @@
+  .syntax unified
+
+  .text
+
+  .global memset_reg
+  .type memset_reg, STT_FUNC
+memset_reg:
+  // call with the following (note that the arguments are not validated prior to use):
+  // r0 - address of first word to write (inclusive)
+  // r1 - address of first word following the address in r0 to NOT write (exclusive)
+  // r2 - word value to be written
+  // both addresses in r0 and r1 needs to be divisible by 4!
+  .L_loop_begin:
+    str r2, [r0], 4 // store the word in r2 to the address in r0, post-indexed
+    cmp r0, r1
+  bne .L_loop_begin
+  bx lr
+
+  .end