common: powerpc: Move arch-specific headers

Set up a new asm/ppc.h header file to hold this arch-specific stuff. It
should not be in common.h. It probably should be refactored to use
asm/arch instead, but that is a job for the maintainer.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/powerpc/include/asm/u-boot.h b/arch/powerpc/include/asm/u-boot.h
index 74b6202..34e44e1 100644
--- a/arch/powerpc/include/asm/u-boot.h
+++ b/arch/powerpc/include/asm/u-boot.h
@@ -16,6 +16,7 @@
 
 /* Use the generic board which requires a unified bd_info */
 #include <asm-generic/u-boot.h>
+#include <asm/ppc.h>
 
 /* For image.h:image_check_target_arch() */
 #define IH_ARCH_DEFAULT IH_ARCH_PPC