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>