nodedev: add PostParse callback for nodedev parsing

nodedev: add PostParse callback for nodedev parsing

This can be used similarly to other postparse callbacks in libvirt --
filling in additional information that can be determined by using the
information provided in the XML. In this case, we determine the address
of the parent device and cache it in the mdev caps so that we can use it
for generating a unique name and interacting with mdevctl.

Signed-off-by: Jonathon Jongsma <jjongsma@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>