[PATCH 2/2] rust: device: make example buildable

[Miguel Ojeda <ojeda@kernel.org>]

This example can easily be made buildable, thus do so.

It would have triggered an `unreachable_pub` warning without the previous
commit.

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 rust/kernel/device.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index a849b7dde2fd..d00f4af507db 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -67,7 +67,16 @@
 ///
 /// A bus specific device should be defined as follows.
 ///
-/// ```ignore
+/// ```
+/// # use core::marker::PhantomData;
+/// # use kernel::{
+/// #     device,
+/// #     types::Opaque, //
+/// # };
+/// # mod bindings {
+/// #     #[expect(non_camel_case_types)]
+/// #     pub struct bus_device_type;
+/// # }
 /// #[repr(transparent)]
 /// pub struct Device<Ctx: device::DeviceContext = device::Normal>(
 ///     Opaque<bindings::bus_device_type>,
-- 
2.51.2