libfdt: split fdt_region declarations out to <fdt_region.h>

fdt_region APIs are not part of libfdt. They are U-Boot extension
for the verified boot. Split the declarations related to fdt_region
out of <fdt_region.h>. This allows <linux/libfdt.h> to become a
simple wrapper file, like Linux does.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
diff --git a/tools/image-host.c b/tools/image-host.c
index 5bb6896..9a83b7f 100644
--- a/tools/image-host.c
+++ b/tools/image-host.c
@@ -10,6 +10,7 @@
 
 #include "mkimage.h"
 #include <bootm.h>
+#include <fdt_region.h>
 #include <image.h>
 #include <version.h>