ARM: prepare for including <mach/*.h>

This commit adds $(srctree)/arch/arm/$(machdirs)/include/mach to
the headers search path.

It allows us to replace "#include <asm/arch/foo.h>" with
"#include <mach/foo.h>".  As "#include <asm/arch/foo.h>" is still
supported, we can modify each file one by one.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 678ac13..878ae26 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -19,6 +19,8 @@
 
 machdirs := $(patsubst %,arch/arm/mach-%/,$(machine-y))
 
+PLATFORM_CPPFLAGS += $(patsubst %,-I$(srctree)/%include,$(machdirs))
+
 libs-y += $(machdirs)
 
 head-y := arch/arm/cpu/$(CPU)/start.o