libfdt: Sync up with upstream

This includes small changes to the following functions, from upstream
commit 6d1832c:

- fdt_get_max_phandle() (upstream commit 84e0e134)
- fdt_node_check_compatible (upstream commit 53bf130b)
- fdt_setprop_inplace_namelen_partial() to remove useless brackets and
     use idx instead of index
- _fdt_resize_property() to use idx instead of index
- _fdt_splice() (upstream commit d4c7c25c)

It also includes various typo fixes in libfdt.h

Signed-off-by: Simon Glass <sjg@chromium.org>