lib: libfdt: fdt_region: avoid NULL pointer access

lib: libfdt: fdt_region: avoid NULL pointer access

The function fdt_find_regions look in the exclude list for each
property, even if the name is NULL. It could happen if the fit
image is corrupted. On sandbox, it generates a segfault.

To avoid this issue, if the name of a property is NULL, we report
an error and avoid looking in the exclude list.

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
Reviewed-by: Simon Glass <sjg@chromium.org>