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/lwmon5/sdram.c b/board/lwmon5/sdram.c
index a482387..f90efeb 100644
--- a/board/lwmon5/sdram.c
+++ b/board/lwmon5/sdram.c
@@ -35,7 +35,7 @@
 #include <asm/mmu.h>
 #include <asm/io.h>
 #include <asm/cache.h>
-#include <ppc440.h>
+#include <asm/ppc440.h>
 #include <watchdog.h>
 
 /*