vfio: Move the PCI implementation to the PCI crate

There is a much stronger PCI dependency from vfio_pci.rs than a VFIO one
from pci/src/vfio.rs. It seems more natural to have the PCI specific
VFIO implementation in the PCI crate rather than the other way around.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

pci/src/lib.rs

@@ -17,6 +17,7 @@ mod configuration;
 mod device;
 mod msi;
 mod msix;
+mod vfio;
 
 pub use self::bus::{PciBus, PciConfigIo, PciConfigMmio, PciRoot, PciRootError};
 pub use self::configuration::{
@@ -29,6 +30,7 @@ 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};
 
 /// PCI has four interrupt pins A->D.
 #[derive(Copy, Clone)]