rust: fs: update ARef and AlwaysRefCounted imports from sync::aref

Update call sites in the fs subsystem to import `ARef` and
`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: Rust-for-Linux#1173
Acked-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Shankari Anand <shankari.ak0208@gmail.com>
Link: https://lore.kernel.org/20250814100101.304408-1-shankari.ak0208@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Shankari02

rust/kernel/fs/file.rs

@@ -11,7 +11,8 @@ use crate::{
     bindings,
     cred::Credential,
     error::{code::*, Error, Result},
-    types::{ARef, AlwaysRefCounted, NotThreadSafe, Opaque},
+    sync::aref::{ARef, AlwaysRefCounted},
+    types::{NotThreadSafe, Opaque},
 };
 use core::ptr;