libfdt: move working_fdt and FDT_RAMDISK_OVERHEAD to include/libfdt.h

libfdt_env.h exists to contain system-dependent defines:

  - typedef of fdt*_t
  - fdt*_to_cpu(), cpu_to_fdt*

working_fdt and FDT_RAMDISK_OVERHEAD are unrelated to the environment,
so they must get out of this header.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/include/libfdt.h b/include/libfdt.h
index 7ba13e6..dbc56ec 100644
--- a/include/libfdt.h
+++ b/include/libfdt.h
@@ -1 +1,14 @@
+#ifndef UBOOT_LIBFDT_H
+#define UBOOT_LIBFDT_H
+/*
+ * SPDX-License-Identifier:     GPL-2.0+ BSD-2-Clause
+ */
+
 #include "../lib/libfdt/libfdt.h"
+
+extern struct fdt_header *working_fdt;	/* Pointer to the working fdt */
+
+/* adding a ramdisk needs 0x44 bytes in version 2008.10 */
+#define FDT_RAMDISK_OVERHEAD	0x80
+
+#endif /* UBOOT_LIBFDT_H */