FS#10756 - Free unused init code

Introduce a new .init section for initialisation code, so that it can be copied to an area which is later overwritten before calling. The stack/bss can then overwrite that code, effectively freeing the code size that the initialisation routines need. Gives a few kB ram usage back.
Only implemented for PP and as3525 so far. More targets could be added, as well as more functions.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@25013 a1c6a512-1295-4272-9138-f99709370657

firmware/target/arm/as3525/app.lds

@@ -99,6 +99,8 @@ SECTIONS
         _iramend = .;
     } > IRAM AT> DRAM
 
+    _iramcopy = LOADADDR(.iram);
+
     .ibss (NOLOAD) :
     {
         _iedata = .;
@@ -108,9 +110,17 @@ SECTIONS
         _iend = .;
     } > IRAM
 
-    _iramcopy = LOADADDR(.iram);
+    .init ENDAUDIOADDR : 
+    {
+        . = ALIGN(4);
+        _initstart = .;
+        *(.init)
+        _initend = .;
+    } AT> DRAM
 
-    .stack (NOLOAD) :
+    _initcopy = LOADADDR(.init);
+
+    .stack _iramcopy (NOLOAD) :
     {
        *(.stack)
        stackbegin = .;