Merge "Only returns supported mixer attributes for USB output devices." into udc-dev am: 1df77b62

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/23175445



Change-Id: I30ef239ee6455ba05fce539e14d9c130cde55828
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>