binman: Allow zero-length entries to overlap

binman: Allow zero-length entries to overlap

Some binary blobs unfortunately obtain their position in the image from
other binary blobs, such as Intel's 'descriptor'. In this case we cannot
rely on packing to work. It is not possible to produce a valid image in
any case, due to the missing blobs.

Allow zero-length overlaps so that this does not cause any problems.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>