readelf: Print DIE offset in attribute reading error messages.

When processing large files it is useful to know the DIE offset if
printing of attributes fails (especially when redirecting the output).
With this change the error message looks like:

  eu-readelf: DIE [2aeb8ef1] cannot get attribute value: invalid DWARF

Signed-off-by: Mark Wielaard <mark@klomp.org>
2 files changed