pci: Address Rust 1.51.0 clippy issue (upper_case_acroynms)

warning: name `IORegion` contains a capitalized acronym
   --> pci/src/configuration.rs:320:5
    |
320 |     IORegion = 0x01,
    |     ^^^^^^^^ help: consider making the acronym lowercase, except the initial letter (notice the capitalization): `IoRegion`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#upper_case_acronyms

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

pci/src/lib.rs

@@ -21,7 +21,7 @@ mod vfio;
 
 pub use self::bus::{PciBus, PciConfigIo, PciConfigMmio, PciRoot, PciRootError};
 pub use self::configuration::{
-    PciBarConfiguration, PciBarPrefetchable, PciBarRegionType, PciCapability, PciCapabilityID,
+    PciBarConfiguration, PciBarPrefetchable, PciBarRegionType, PciCapability, PciCapabilityId,
     PciClassCode, PciConfiguration, PciHeaderType, PciMassStorageSubclass,
     PciNetworkControllerSubclass, PciProgrammingInterface, PciSerialBusSubClass, PciSubclass,
 };