* Offset pci_device_id for network devices by 32 (formerly 4)
to reserve first 32 IDs for non-netdev devices
* This implies a new pci_bridge for the netdevs and
the pci_device_ids starting at 0 (using modulo)
* Fixes a bug in the creation of the qemu command
when the number of qemu pcie devices (storage_controller, disks, …)
was greater than 4 and the number of network devices
saturated the 32 pcie ids of the root bridge
causing qemu not to start.