[automerger skipped] audio: Simplify and extend alsa::Mixer am: d21b0e7e -s ours

am skip reason: Merged-In I0fad994153de96aceec3eb8f2fec19805ec912f8 with SHA-1 f12d4a1e is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/hardware/interfaces/+/24287962



Change-Id: I029f7959b1c916a4c09799a9ce1fa667f1382fdf
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>