device: virtio: video: Add dead_code attribute to SetControl

BUG=b:161774071
TEST=None

Change-Id: Ia9c9ba1a316a409c17ac601e94bd3f6a75b24af5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2355847
Tested-by: Alex Lau <alexlau@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-by: Alexandre Courbot <acourbot@chromium.org>
Commit-Queue: Keiichi Watanabe <keiichiw@chromium.org>
diff --git a/devices/src/virtio/video/response.rs b/devices/src/virtio/video/response.rs
index 3502957..5ee74ff 100644
--- a/devices/src/virtio/video/response.rs
+++ b/devices/src/virtio/video/response.rs
@@ -45,6 +45,8 @@
     },
     QueryControl(QueryCtrlResponse),
     GetControl(CtrlVal),
+    // TODO(alexlau): SetControl is unused, remove this after encoder CL lands.
+    #[allow(dead_code)]
     SetControl,
     Error(CmdError),
 }