Merge "audio: Clarify comments on AudioPortMixExt fields" am: 58e6e6d448 am: cc304e90cf

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

Change-Id: I6c1bf9dfab028c0a6949297b5cc6e6a04a310ccb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>