Guest SR-IOV: Replace previous changeset with a more complete implementation from...

Guest SR-IOV: Replace previous changeset with a more complete implementation from Intel

"""Guest SR-IOV support for PV guest

These changes are for PV guest to use Virtual Function. Because the
VF's vendor, device registers in cfg space are 0xffff, which are
invalid and ignored by PCI device scan. Values in 'struct pci_dev' are
fixed up by SR-IOV code, and using these values will present correct
VID and DID to PV guest kernel.

And command registers in the cfg space are read only 0, which means we
have to emulate MMIO enable bit (VF only uses MMIO resource) so PV
kernel can work properly."""

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>