add api for aux command buffer flush am: 33912d7871 am: d5a5685364

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

Change-Id: I332b75b566130ccd16bf0ba94f9b41583b32dc16
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>