Provide option to bind VFs to vfio driver

[byteocean]

#680

This enhanced init script provides extra steps to manually bind VFs to vfio-pci driver, which is automatically done by libvirt.

There are two ways to use this feature:

1. after rebooting, use this script with --vfio-auto-bind. It creates VFs binding to vfio-pci;
2. if you already have VFs, terminate/undefine all VMs, and run this script with --vfio-bind-only, it will do binding only.

[PlagueCZ]

Seems the best way to implement this, just some small details I would address.

[PlagueCZ]

Looks great now.
Did not test on my hardware though.