Merge "audio: Clarify comments on AudioPortMixExt fields" am: 58e6e6d448

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2191216

Change-Id: I48be75318780893b61e88742324db0708cd4f7a6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>