hal: policy: fallback to deep buffer if stream is music

- in case of direct PCM, Direct flag is added explicitly which
  is causing deep buffer flag not to be added for Music case.
- absence of deep buffer flag is causing low latency path to be
  selected by default if direct pcm fails. Fastmixer path has
  higher power footprint.
- to avoid low latency and allow stream music to use deep buffer path
  check if direct flag is added explicitly, if so allow adding
  deep buffer flag. This will allow selecting deep buffer output.

Change-Id: Icc1de9f4ac3ff7981d2325fbda4891d9b8476df7