rust: usb: Update AlwaysRefCounted imports to use sync::aref

Update call sites in `usb.rs` to import `AlwaysRefCounted`
from `sync::aref` instead of `types`.

This aligns with the ongoing effort to move `ARef` and
`AlwaysRefCounted` to sync.

Suggested-by: Benno Lossin <lossin@kernel.org>
Link: #1173
Signed-off-by: Shankari Anand <shankari.ak0208@gmail.com>
Link: https://patch.msgid.link/20260102202714.184223-4-shankari.ak0208@gmail.com
[ Rebase. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: Shankari02

rust/kernel/usb.rs

@@ -18,10 +18,8 @@ use crate::{
         to_result, //
     },
     prelude::*,
-    types::{
-        AlwaysRefCounted,
-        Opaque, //
-    },
+    sync::aref::AlwaysRefCounted,
+    types::Opaque,
     ThisModule, //
 };
 use core::{