add api for aux command buffer flush am: 33912d7871

Original change: https://android-review.googlesource.com/c/platform/external/gfxstream-protocols/+/2377332

Change-Id: I30f6074e2445329eadf2a30e42a9cadfc7d2a0f3
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>