ASoC: msm: Fix delay in switching from WFD session

- When a running WFD session is paused/disconnected, there is
  a delay of about 10-15 seconds in switching audio from WFD
  sink to target.
- pcm_write is blocked because pausing/disconnecting the WFD
  session closes the backend DAI before a new link is established.
- Avoid closing afe if front end PCM session is still active.

CRs-Fixed: 444163
CRs-Fixed: 425512
Change-Id: I1ad6de1e201aa6130c397007219c0d370c7be2a1
Signed-off-by: Satya Krishna Pindiproli <satyak@codeaurora.org>