audiopolicy: remove soundcard status check from isOffloadSupported()

- Attempt to get sound card status from isOffloadSupported() can
  cause cross deadlock if audio flinger calls other audio policy
  APIs concurrently to update effect status with AudioFlinger's
  mLock already acquired.
- Also fetching sound card status from the context of
  isOffloadSupported() is not necessary as even though offload is
  marked supported here, error from request to open audio output
  would always make player fallback to non offload path.

CRs-Fixed: 1048043
Change-Id: I95cd3310da130deb1e6b3847bd6af79f15dd7415