Remove AudioMixLatencyClass enum from AIDL interfaces

The enum was only used for the 'AudioPortMixExt.latencyClass'
field, which is "write only" on the framework side, and isn't
used on the HAL side.

Bug: 198812639
Test: m
Change-Id: Ibf245027696e4df1df6f434b9553012461f90b7b
6 files changed