hal: Fix WFD and voice call over USB concurrency

- If WFD framework occupies the AFE proxy, it may result unintended
  behavior while starting voice call over USB.
- Audio is always routed to the USB audio device when connected,
  even if WFD is connected. So no need to allow afe proxy port
  usage by WFD framework.
- Disallow the afe proxy port usage by external modules when
  AUDIO_DEVICE_OUT_USB_DEVICE is connected.

CRs-Fixed: 998488

Change-Id: I889be7f477ae3f7ad46757592a46f3d0e8eb41e2
diff --git a/hal/audio_hw.h b/hal/audio_hw.h
index a7d4483..e13415d 100644
--- a/hal/audio_hw.h
+++ b/hal/audio_hw.h
@@ -323,6 +323,7 @@
     unsigned int cur_hdmi_channels;
     unsigned int cur_wfd_channels;
     bool bt_wb_speech_enabled;
+    bool allow_afe_proxy_usage;
 
     int snd_card;
     unsigned int cur_codec_backend_samplerate;