`#[derive(HasField)]` offers less code and better ergnomic for defining
a struct with a Work in it. Hence replace the current usage of
`impl_has_work!()`.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
 rust/kernel/sync/completion.rs | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/rust/kernel/sync/completion.rs b/rust/kernel/sync/completion.rs
index c50012a940a3..c4af58924fe3 100644
--- a/rust/kernel/sync/completion.rs
+++ b/rust/kernel/sync/completion.rs
@@ -17,20 +17,18 @@
 ///
 /// ```
 /// use kernel::sync::{Arc, Completion};
-/// use kernel::workqueue::{self, impl_has_work, new_work, Work, WorkItem};
+/// use kernel::workqueue::{self, new_work, Work, WorkItem};
 ///
+/// #[derive(HasField)]
 /// #[pin_data]
 /// struct MyTask {
 ///     #[pin]
+///     #[field]
 ///     work: Work<MyTask>,
 ///     #[pin]
 ///     done: Completion,
 /// }
 ///
-/// impl_has_work! {
-///     impl HasWork<Self> for MyTask { self.work }
-/// }
-///
 /// impl MyTask {
 ///     fn new() -> Result<Arc<Self>> {
 ///         let this = Arc::pin_init(pin_init!(MyTask {
-- 
2.50.1 (Apple Git-155)