hal: Define AUDIO_OUTPUT_FLAG_COMPRESS_PASSTHROUGH

* On every other branch this flag was added at this location with commit
  b27354b1 "hal: compilation fix for extended feature flags",
  however for LA.BF64.1.2.X, the equivalent commit:
  d5144f14 "hal: compilation fix for extended feature flags"
  did not add it, resulting from a prior divergence. Re-add the flag manually,
  since it is expected that the HAL provides this definition.
* LA.BF64, LA.BR generation HALs are not expected to have moved this
  flag to the current location as found in LA.UM.5.X HALs as they are not
  expected to have the following commits:
    21854657 "hal: add support for compress passthrough"
    cb6212e0 "hal: Add support for native-DSD and native sampling rates"
    591c2baf "qahw: test: Add support for playback of more file types"

Change-Id: I3e5aba03faaf6a878c7c914a57a47170b3ee18d8