binman: Avoid reporting image-pos with compression

binman: Avoid reporting image-pos with compression

When a section is compressed, all entries within it are grouped together
into a compressed block of data. This obscures the start of each
individual child entry.

Avoid reporting bogus 'image-pos' properties in this case, since it is
not possible to access the entry at the location provided. The entire
section must be decompressed first.

CBFS does not support compressing whole sections, only individual files,
so needs no special handling here.

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