hal: Fix for VoIP call audio mode switch bug

- Audio mode switch between speaker and headset fails during a VoIP call
- This is because only one request is allowed by APM with Direct/VoIP
  flag to get VoIP usecase in HAL.
- If another VoIP request comes in while a VoIP session is still open,
  then the request falls back and is treated as a request for primary
  output with NONE flag.
- And if there are no low-latency sessions open and any previously
  active VoIP session is closed, then the latter VoIP request handles
  routing for primary output.
- The fix allows VoIP usecase to handle routing properly when using
  primary output.

CRs-Fixed: 2000184
Change-Id: Ibda10fe0de64f33ad34340dd0ff3b710918c4461