audio: remove unused struct member

Removed unused member out_device from struct audio_device.

Change-Id: Id5ae06aed7d38aa85aefe09b9ff733bde1e52f57
diff --git a/hal/audio_hw.c b/hal/audio_hw.c
index 48c426d..972837b 100644
--- a/hal/audio_hw.c
+++ b/hal/audio_hw.c
@@ -2356,7 +2356,6 @@
     adev->mode = AUDIO_MODE_NORMAL;
     adev->active_input = NULL;
     adev->primary_output = NULL;
-    adev->out_device = AUDIO_DEVICE_NONE;
     adev->voice_call_rx = NULL;
     adev->voice_call_tx = NULL;
     adev->voice_volume = 1.0f;
diff --git a/hal/audio_hw.h b/hal/audio_hw.h
index 0da4324..e2d6ff7 100644
--- a/hal/audio_hw.h
+++ b/hal/audio_hw.h
@@ -173,7 +173,6 @@
     pthread_mutex_t lock; /* see note below on mutex acquisition order */
     struct mixer *mixer;
     audio_mode_t mode;
-    audio_devices_t out_device;
     struct stream_in *active_input;
     struct stream_out *primary_output;
     int in_call;