audio: Update README.md to add info about the AIDL version

Commit hashes mismatch is intentional, it seems that the previous
upstreaming left some of the downstream changes out.

Bug: 205884982
Test: N/A
Change-Id: Ia1a7879ae538a4e90aee62f9050b9d22ffa64fe7
Merged-In: Ia627e3845a078e6a4c545b13a723a6c5a038c53b