audiolayer: don't lock in putUrgent

RingBuffer has its own mutex. This avoids potential deadlocks.

Change-Id: I93175aafe9fbb3f927da28124a7d42e61585523d

src/media/audio/audiolayer.cpp

@@ -156,7 +156,6 @@ AudioLayer::checkAEC()
 void
 AudioLayer::putUrgent(AudioBuffer& buffer)
 {
-    std::lock_guard<std::mutex> lock(mutex_);
     urgentRingBuffer_.put(buffer.toAVFrame());
 }