Merge "audio: Clarify comments on AudioPortMixExt fields" am: 58e6e6d448 am: cc304e90cf am: 94cbc8191f am: 4965ef5e89

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

Change-Id: I4c6ba50074b1eb93742eab2e67317426677f39d2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>