Flag these three as allowed to be unused to make crosvm warning-free
again.
Change-Id: Id9bf18728c481484e31860836de6f0a1d1e55c5a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1988282
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Tested-by: Dylan Reid <dgreid@chromium.org>
Commit-Queue: Dylan Reid <dgreid@chromium.org>