WS: temporarily set default CCA threshold to -80 (ARMmbed#2431)

Author: Jarkko Paso

source/6LoWPAN/ws/ws_common_defines.h

@@ -332,7 +332,7 @@ typedef struct ws_bs_ie {
 /*
  * Automatic CCA threshold: default threshold and range in dBm.
  */
-#define CCA_DEFAULT_DBM -60
+#define CCA_DEFAULT_DBM -80
 #define CCA_HIGH_LIMIT  -60
 #define CCA_LOW_LIMIT   -100