arm: Move cpu/$CPU to arch/arm/cpu/$CPU

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/doc/README.modnet50 b/doc/README.modnet50
index f7bb254..2ac3c8f 100644
--- a/doc/README.modnet50
+++ b/doc/README.modnet50
@@ -45,7 +45,7 @@
 
 Files:
 
-cpu/arm720t/serial_netarm.c .. serial I/O for the cpu
+arch/arm/cpu/arm720t/serial_netarm.c .. serial I/O for the cpu
 
 board/modnet50/lowlevel_init.S   .. memory setup for ModNET50
 board/modnet50/flash.c	    .. flash routines