pci: Add support for vfio-user PCI devices

Taking advantage of the refactored VFIO code implement a new
VfioUserPciDevice that wraps the client for vfio-user and exposes the
BusDevice and PciDevice into the VMM.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

pci/src/lib.rs

@@ -12,6 +12,7 @@ mod device;
 mod msi;
 mod msix;
 mod vfio;
+mod vfio_user;
 
 pub use self::bus::{PciBus, PciConfigIo, PciConfigMmio, PciRoot, PciRootError};
 pub use self::configuration::{
@@ -25,6 +26,7 @@ pub use self::device::{
 pub use self::msi::{msi_num_enabled_vectors, MsiCap, MsiConfig};
 pub use self::msix::{MsixCap, MsixConfig, MsixTableEntry, MSIX_TABLE_ENTRY_SIZE};
 pub use self::vfio::{VfioPciDevice, VfioPciError};
+pub use self::vfio_user::{VfioUserPciDevice, VfioUserPciDeviceError};
 
 /// PCI has four interrupt pins A->D.
 #[derive(Copy, Clone)]