hal: mute stream and switch to speaker during a2dp suspend

During A2DP to SCO transition, in order to avoid audible
PCM data pumping to BT SoC during suspend, mute stream
from DSP and switch to speaker to tear down slimbus to
avoid glitches heard after SCO connection is established.

Change-Id: Iabe2216e574b462cfc179369e75007998a576480
diff --git a/hal/audio_hw.h b/hal/audio_hw.h
index f1e8672..32271bb 100644
--- a/hal/audio_hw.h
+++ b/hal/audio_hw.h
@@ -442,7 +442,7 @@
     qahwi_stream_out_t qahwi_out;
 
     bool is_iec61937_info_available;
-    bool a2dp_compress_mute;
+    bool a2dp_muted;
     float volume_l;
     float volume_r;
     bool apply_volume;