policy_hal: Correct device selection in STRATEGY_ENFORCED_AUDIBLE

- When strategy is STRATEGY_ENFORCED_AUDIBLE, do not select
  unsupported combo devices Proxy+Speaker, HDMI+Speaker,
  and FM_TX + Speaker.

Change-Id: Icd4f6de74807a6efc5f6eb8258c020ad990aaf9b
Crs-fixed: 600799