system: Allow some fields to never be read

It's a common pattern in tacd codebase to collect all Topics
in a struct to make them available to e.g. the UI code.
These fields are not used, but should nevertheless be stored
in the respective struct to keep the common pattern.

Signed-off-by: Leonard Göhrs <[email protected]>

Author: hnez

src/system.rs

@@ -134,8 +134,11 @@ impl Barebox {
 }
 
 pub struct System {
+    #[allow(dead_code)]
     pub uname: Arc<Topic<Arc<Uname>>>,
+    #[allow(dead_code)]
     pub barebox: Arc<Topic<Arc<Barebox>>>,
+    #[allow(dead_code)]
     pub tacd_version: Arc<Topic<String>>,
 }