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/drivers/i2c/ppc4xx_i2c.c b/drivers/i2c/ppc4xx_i2c.c
index e9548f1..c1cbe55 100644
--- a/drivers/i2c/ppc4xx_i2c.c
+++ b/drivers/i2c/ppc4xx_i2c.c
@@ -27,8 +27,8 @@
  */
 
 #include <common.h>
-#include <ppc4xx.h>
-#include <4xx_i2c.h>
+#include <asm/ppc4xx.h>
+#include <asm/ppc4xx-i2c.h>
 #include <i2c.h>
 #include <asm/io.h>