rust: devres: provide an accessor for the device

Provide an accessor for the Device a Devres instance has been created
with.

For instance, this is useful when registrations want to provide a
&Device<Bound> for a scope that is protected by Devres.

Suggested-by: Benno Lossin <[e-mail]>
Acked-by: Greg Kroah-Hartman <[e-mail]>
Reviewed-by: Benno Lossin <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Danilo Krummrich <[e-mail]>

rust/kernel/devres.rs

···
         } == 0)
     }
 
+    /// Return a reference of the [`Device`] this [`Devres`] instance has been created with.
+    pub fn device(&self) -> &Device {
+        &self.dev
+    }
+
     /// Obtain `&'a T`, bypassing the [`Revocable`].
     ///
     /// This method allows to directly obtain a `&'a T`, bypassing the [`Revocable`], by presenting