[#3052] Use Celt 32000 with 320 frame size

sflphone-common/src/audio/codecs/celtcodec.cpp

@@ -29,7 +29,7 @@ class Celt : public AudioCodec
         Celt (int payload=0)	: AudioCodec (payload, "celt") {
 
             _clockRate = 32000;
-            _frameSize = 512;  // fixed frameSize, TODO: support variable size from 64 to 512
+            _frameSize = 320;  // fixed frameSize, TODO: support variable size from 64 to 512
             _channel = 1;
             _bitrate = 0;
             _bandwidth = 0;