devices: pci: add domain to PciAddress fmt output

This was accidentally omitted in the original change. Add some basic
tests to make sure it doesn't regress.

BUG=None
TEST=cargo test -p devices pci_address

Change-Id: Iaedf2357ae02d6203e8296e9765f5ce3bf5bdc84
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3534507
Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>

devices/src/pci/pci_address.rs

@@ -41,7 +41,12 @@ pub struct PciAddress {
 
 impl Display for PciAddress {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{:04x}:{:02x}.{:0x}", self.bus, self.dev, self.func)
+        let domain = 0;
+        write!(
+            f,
+            "{:04x}:{:02x}:{:02x}.{:0x}",
+            domain, self.bus, self.dev, self.func,
+        )
     }
 }
 
@@ -284,4 +289,20 @@ mod tests {
             Error::ComponentOutOfRange(PciAddressComponent::Domain)
         );
     }
+
+    #[test]
+    fn format_simple() {
+        assert_eq!(
+            PciAddress::new(0, 1, 2, 3).unwrap().to_string(),
+            "0000:01:02.3"
+        );
+    }
+
+    #[test]
+    fn format_max() {
+        assert_eq!(
+            PciAddress::new(0, 0xff, 0x1f, 7).unwrap().to_string(),
+            "0000:ff:1f.7"
+        );
+    }
 }