audiopolicy: Use AUDIO_OUTPUT_FLAG_TTS for TTS stream

Use AUDIO_OUTPUT_FLAG_TTS by default for TTS stream to see
if the HW supports a dedicated output for the same. If not,
fallback to primary output as it is done currently.

Change-Id: Ifb2ef7066e75c61fe4c1b9783c12627386a00ea5
diff --git a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
index 0c02d93..d1ee400 100644
--- a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
+++ b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
@@ -768,6 +768,9 @@
     if (stream != AUDIO_STREAM_MUSIC) {
         flags = (audio_output_flags_t)(flags &~AUDIO_OUTPUT_FLAG_DEEP_BUFFER);
     }
+    if (stream == AUDIO_STREAM_TTS) {
+        flags = AUDIO_OUTPUT_FLAG_TTS;
+    }
 
     sp<IOProfile> profile;