【修改默认音频输出为Speaker】

机型无听筒，只有扬声器，需要把音频输出修改为speaker

1. services/audiopolicy/enginedefault/src/Engine.cpp

   devices = availableOutputDevices.getDevicesFromType(AUDIO_DEVICE_OUT_EARPIECE);
   修改为：
   // set the speaker as default mode
   devices = availableOutputDevices.getDevicesFromType(AUDIO_DEVICE_OUT_SPEAKER);
   

2. services/core/java/com/android/server/audio/AudioDeviceBroker.java

    
   boolean isSpeakerphoneOn() {
       synchronized (mDeviceStateLock) {
   		if (AudioService.DEBUG_SCO) {
           	Log.i(TAG, "In isSpeakerphoneOn(), mForcedUseForCommExt: " +mForcedUseForCommExt);
           }
           return (mForcedUseForCommExt == AudioSystem.FORCE_SPEAKER || mForcedUseForCommExt == AudioSystem.FORCE_NONE);
   	}
   }