[rialto] Find virtio socket device through PCI bus

Bug: 284462758
Test: atest rialto_test
Change-Id: I62836d42b6afba2beea37ef57e8745f03e6d0c3d
diff --git a/rialto/src/error.rs b/rialto/src/error.rs
index c326566..0c1e25d 100644
--- a/rialto/src/error.rs
+++ b/rialto/src/error.rs
@@ -37,6 +37,10 @@
     MemoryOperationFailed(MemoryTrackerError),
     /// Failed to initialize PCI.
     PciInitializationFailed(pci::PciError),
+    /// Failed to create VirtIO Socket device.
+    VirtIOSocketCreationFailed(virtio_drivers::Error),
+    /// Missing socket device.
+    MissingVirtIOSocketDevice,
 }
 
 impl fmt::Display for Error {
@@ -50,6 +54,10 @@
             Self::InvalidPci(e) => write!(f, "Invalid PCI: {e}"),
             Self::MemoryOperationFailed(e) => write!(f, "Failed memory operation: {e}"),
             Self::PciInitializationFailed(e) => write!(f, "Failed to initialize PCI: {e}"),
+            Self::VirtIOSocketCreationFailed(e) => {
+                write!(f, "Failed to create VirtIO Socket device: {e}")
+            }
+            Self::MissingVirtIOSocketDevice => write!(f, "Missing VirtIO Socket device."),
         }
     }
 }