prepare joining at91rm9200 into at91

* prepare joining at91 and at91rm9200
 * add modified copy of soc files to cpu/arm920t/at91 to make
   possible to compile at91rm9200 boards in at91 tree instead
   of at91rm9200
 * add header files with c structure defs for AT91 MC, ST and TC
 * the new cpu files are using at91 c structure soc access
 * please read README.soc-at91 for details

Signed-off-by: Jens Scharsig <js_at_ng@scharsoft.de>
diff --git a/cpu/arm920t/cpu.c b/cpu/arm920t/cpu.c
index 34adb11..be82c87 100644
--- a/cpu/arm920t/cpu.c
+++ b/cpu/arm920t/cpu.c
@@ -33,6 +33,10 @@
 #include <command.h>
 #include <asm/system.h>
 
+#ifdef CONFIG_AT91_LEGACY
+#warning Your board is using legacy AT91RM9200 SoC access. Please update!
+#endif
+
 static void cache_flush(void);
 
 int cleanup_before_linux (void)