common: Move device-tree setup functions to fdt_support.h

These functions relate to setting up the device tree for booting the OS.
The fdt_support.h header file supports similar functions, so move these
there.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/keymile/km83xx/km83xx.c b/board/keymile/km83xx/km83xx.c
index feca7be..23bbdcc 100644
--- a/board/keymile/km83xx/km83xx.c
+++ b/board/keymile/km83xx/km83xx.c
@@ -15,6 +15,7 @@
 
 #include <common.h>
 #include <env.h>
+#include <fdt_support.h>
 #include <init.h>
 #include <ioports.h>
 #include <mpc83xx.h>