Add HFP AIDL design am: e50be86fd4 am: fbf5d5c9d7

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2774933

Change-Id: I835b6fa60c246fd375b4d63b181aa768e762ac62
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>