audio: Refactor Mmap buffer creation and handling am: b0a3695b76

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/3550139

Change-Id: I519f26ecf1698f5705f8809a559ec094b904b579
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>