audio: fix stream type for accessibility usage

Make sure that accessibility prompts are heard when
a ringtone is active by forcing stream type
to AUDIO_STREAM_RING when phone state is AUDIO_MODE_RINGTONE.

Bug: 17558149.
Change-Id: Ia3bead8052fca5cbf282c267f7b9b06014fef628
diff --git a/include/media/IAudioPolicyService.h b/include/media/IAudioPolicyService.h
index c251439..16fe9cf 100644
--- a/include/media/IAudioPolicyService.h
+++ b/include/media/IAudioPolicyService.h
@@ -142,6 +142,8 @@
                                            audio_devices_t *device) = 0;
 
     virtual status_t releaseSoundTriggerSession(audio_session_t session) = 0;
+
+    virtual audio_mode_t getPhoneState() = 0;
 };