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/arch/powerpc/cpu/ppc4xx/start.S b/arch/powerpc/cpu/ppc4xx/start.S
index 4bad32f..fcef0c2 100644
--- a/arch/powerpc/cpu/ppc4xx/start.S
+++ b/arch/powerpc/cpu/ppc4xx/start.S
@@ -64,7 +64,7 @@
  *  address and (s)dram will be positioned at address 0
  */
 #include <config.h>
-#include <ppc4xx.h>
+#include <asm/ppc4xx.h>
 #include <timestamp.h>
 #include <version.h>