libfdt: Make fdtdec_get_child_count() available for HOST
The tool need to use fdtdec_get_child_count(), make it available for
HOST_CC.
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
Reviewed-by: Simon Glass <sjg@chromium.org>