conf: Reintroduce action to virDomainDefCompatibleDevice
    
    This was lost in c57f3fd2f8999d17e01. But now we are going to
    need it again (except the DETACH action where checking for device
    compatibility does not make much sense anyway).
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
    Reviewed-by: John Ferlan <jferlan@redhat.com>