drm/asahi: File: Clippy fixes

Signed-off-by: Asahi Lina <lina@asahilina.net>

Author: hoshinolina

drivers/gpu/drm/asahi/file.rs

@@ -1093,7 +1093,7 @@ impl File {
                 );
                 Err(e)
             }
-            Ok(_) => Ok(0),
+            Ok(()) => Ok(0),
         }
     }