qemu.tests.pci_devices: Support for lspci verification

Hi guys,

this patch adds support to verify info from guest `lspci` with info from host `info qtree` to pci_devices test. Please note that all test probably fails as a bit funny bug was found while developing this. When you boot VM with `-S` the PCI addresses of devices in bridge/switch in info qtree are messed up... (when you force autotest to run without `-S` the test passes).

Kind regards,
Lukáš