ppc4xx: Move ppc4xx headers to powerpc include directory

This patch moves some ppc4xx related headers from the common include
directory (include/) to the powerpc specific one
(arch/powerpc/include/asm/). This way to common include directory is not
so cluttered with files.

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/board/amcc/redwood/redwood.c b/board/amcc/redwood/redwood.c
index 32fb8c5..bb7565e 100644
--- a/board/amcc/redwood/redwood.c
+++ b/board/amcc/redwood/redwood.c
@@ -26,7 +26,7 @@
 
 #include <common.h>
 #include "redwood.h"
-#include <ppc4xx.h>
+#include <asm/ppc4xx.h>
 #include <asm/processor.h>
 #include <i2c.h>
 #include <asm/io.h>