feat(xen): update xenclient and xenplatform to the latest structure (#433)

crates/xen/xenclient/src/util.rs

@@ -0,0 +1,21 @@
+use crate::error::{Error, Result};
+
+pub fn vbd_blkidx_to_disk_name(blkid: u32) -> Result<String> {
+    let mut name = "xvd".to_string();
+    let mut suffix = String::new();
+    let mut n = blkid;
+    loop {
+        let c = (n % 26) as u8;
+        let c = b'a' + c;
+        let c = char::from_u32(c as u32).ok_or(Error::InvalidBlockIdx)?;
+        suffix.push(c);
+        if n >= 26 {
+            n = (n / 26) - 1;
+            continue;
+        } else {
+            break;
+        }
+    }
+    name.push_str(&suffix.chars().rev().collect::<String>());
+    Ok(name)
+}