libfdt: update fdt.h from upstream dtc

upstream dtc commit feafcd972cb744750a65728440c99526e6199a6d
"dtc/libfdt: introduce fdt types for annotation by endian checkers".

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Cc: Jerry Van Baren <gvb.uboot@gmail.com>