Merge "Allow to register RENDER AudioMix pointing to previously registered LOOPBACK AudioMix." into udc-dev am: 55825ec1 am: 8a9bce9a

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/23693534



Change-Id: I6479243820a7c9ba39e88293c5e2b613b2a1261f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>