elf2dmp: replace PE export name check with PDB name check

PE export name check introduced in d399d6b1 isn't reliable enough,
because a page with the export directory may be not present for some
reason. On the other hand, elf2dmp retrieves the PDB name in any case.
It can be also used to check that a PE image is the kernel image. So,
check PDB name when searching for Windows kernel image.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2165917



Signed-off-by: Viktor Prutyanov <viktor@daynix.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-id: 20230915170153.10959-2-viktor@daynix.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>