lib: libfdt: wrap scripts/dtc/libfdt/* where possible

lib/libfdt/ and scripts/dtc/libfdt have the same copies for the
followings 6 files:
  fdt.c fdt_addresses.c fdt_empty_tree.c fdt_overlay.c fdt_strerr.c
  fdt_sw.c

Make them a wrapper of scripts/dtc/libfdt/*.  This is exactly what
Linux does to sync libfdt.  In order to make is possible, import
<linux/libfdt.h> and <linux/libfdt_env.h> from Linux 4.14-rc5.

Unfortunately, U-Boot locally modified the following 3 files:
  fdt_ro.c fdt_wip.c fdt_rw.c

The fdt_region.c is U-Boot own file.

I did not touch them in order to avoid unpredictable impact.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/lib/libfdt/fdt_strerror.c b/lib/libfdt/fdt_strerror.c
index f89004c..408a883 100644
--- a/lib/libfdt/fdt_strerror.c
+++ b/lib/libfdt/fdt_strerror.c
@@ -1,61 +1,2 @@
-/*
- * libfdt - Flat Device Tree manipulation
- * Copyright (C) 2006 David Gibson, IBM Corporation.
- * SPDX-License-Identifier:	GPL-2.0+ BSD-2-Clause
- */
-#include <libfdt_env.h>
-
-#ifndef USE_HOSTCC
-#include <fdt.h>
-#include <libfdt.h>
-#else
-#include "fdt_host.h"
-#endif
-
-#include "libfdt_internal.h"
-
-struct fdt_errtabent {
-	const char *str;
-};
-
-#define FDT_ERRTABENT(val) \
-	[(val)] = { .str = #val, }
-
-static struct fdt_errtabent fdt_errtable[] = {
-	FDT_ERRTABENT(FDT_ERR_NOTFOUND),
-	FDT_ERRTABENT(FDT_ERR_EXISTS),
-	FDT_ERRTABENT(FDT_ERR_NOSPACE),
-
-	FDT_ERRTABENT(FDT_ERR_BADOFFSET),
-	FDT_ERRTABENT(FDT_ERR_BADPATH),
-	FDT_ERRTABENT(FDT_ERR_BADPHANDLE),
-	FDT_ERRTABENT(FDT_ERR_BADSTATE),
-
-	FDT_ERRTABENT(FDT_ERR_TRUNCATED),
-	FDT_ERRTABENT(FDT_ERR_BADMAGIC),
-	FDT_ERRTABENT(FDT_ERR_BADVERSION),
-	FDT_ERRTABENT(FDT_ERR_BADSTRUCTURE),
-	FDT_ERRTABENT(FDT_ERR_BADLAYOUT),
-	FDT_ERRTABENT(FDT_ERR_INTERNAL),
-	FDT_ERRTABENT(FDT_ERR_BADNCELLS),
-	FDT_ERRTABENT(FDT_ERR_BADVALUE),
-	FDT_ERRTABENT(FDT_ERR_BADOVERLAY),
-	FDT_ERRTABENT(FDT_ERR_NOPHANDLES),
-};
-#define FDT_ERRTABSIZE	(sizeof(fdt_errtable) / sizeof(fdt_errtable[0]))
-
-const char *fdt_strerror(int errval)
-{
-	if (errval > 0)
-		return "<valid offset/length>";
-	else if (errval == 0)
-		return "<no error>";
-	else if (errval > -FDT_ERRTABSIZE) {
-		const char *s = fdt_errtable[-errval].str;
-
-		if (s)
-			return s;
-	}
-
-	return "<unknown error>";
-}
+#include <linux/libfdt_env.h>
+#include "../../scripts/dtc/libfdt/fdt_strerror.c"