* 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>