bufferpool2: add sync() method and etc am: 72b2b38c7f

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2684986

Change-Id: I07ffb9918f51791b70233bc8bc04d4fcb8b90424
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>