audio: Match framework expectations for mic addresses

The framework expects that "built-in mic" has address "bottom",
and the "buitl-in back mic" has address "back". This logic
will be incorporated into the XML to AIDL serializer later.

Bug: 205884982
Test: enable AIDL audio HAL on CF and run `atest CtsMediaAudioTestCases`
Change-Id: I5052b312b673e18e3148f917487b1f90a1e04ba6