runtime-rs: Simplify VhostUserType enum

Remove unused string parameter from each item.

Fixes: #8625

Signed-off-by: Xuewei Niu <niuxuewei.nxw@antgroup.com>

src/runtime-rs/crates/resource/src/volume/direct_volumes/spdk_volume.rs

@@ -75,7 +75,7 @@ impl SPDKVolume {
 
         let vhu_blk_config = &mut VhostUserConfig {
             socket_path: device,
-            device_type: VhostUserType::Blk("vhost-user-blk-pci".to_owned()),
+            device_type: VhostUserType::Blk,
             driver_option: block_driver,
             ..Default::default()
         };