Fix FastMixer high bit depth Hal support

        free(mSinkBuffer);

        mSinkBuffer = NULL;

        if (frameCount > 0 && mSampleRate > 0) {

            // The mixer produces either 16 bit PCM or float output, select

            // float output if the HAL supports higher than 16 bit precision.

            mMixerBufferFormat = mFormat.mFormat == AUDIO_FORMAT_PCM_16_BIT ?

                    AUDIO_FORMAT_PCM_16_BIT : AUDIO_FORMAT_PCM_FLOAT;

            // FIXME new may block for unbounded time at internal mutex of the heap

            //       implementation; it would be better to have normal mixer allocate for us

            //       to avoid blocking here and to prevent possible priority inversion