binman: Handle reading data for end-at-4gb sections

Some x86 sections have special offsets which currently result in empty
data being returned from the 'extract' command. Fix this by taking account
of the skip-at-start property.

Add a little more debugging while we are here.

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