turned on correlator in radio packet filter

Enabling this option seems to greatly improve transciever performance with
Contikimac. This seems to happen because Contikimac CCAs are much less likely
to detect false positives (thus screwing up the CCA sequence).

cpu/cc26xx/dev/cc26xx-rf.c

@@ -892,10 +892,11 @@ init_rf_params(void)
   /* Configure CCA settings */
   GET_FIELD(cmd_ieee_rx_buf, CMD_IEEE_RX, ccaOpt) =
     BITVALUE(CMD_IEEE_RX, ccaOpt, ccaEnEnergy, 1) |
-    BITVALUE(CMD_IEEE_RX, ccaOpt, ccaEnCorr, 0) |
+    BITVALUE(CMD_IEEE_RX, ccaOpt, ccaEnCorr, 1) |
     BITVALUE(CMD_IEEE_RX, ccaOpt, ccaEnSync, 0) |
-    BITVALUE(CMD_IEEE_RX, ccaOpt, ccaCorrOp, 0) |
-    BITVALUE(CMD_IEEE_RX, ccaOpt, ccaSyncOp, 0);
+    BITVALUE(CMD_IEEE_RX, ccaOpt, ccaCorrOp, 1) |
+    BITVALUE(CMD_IEEE_RX, ccaOpt, ccaSyncOp, 1) |
+    BITVALUE(CMD_IEEE_RX, ccaOpt, ccaCorrThr, 3);
   /* Set CCA RSSI Threshold, 0xA6 corresponds to -90dBm (two's comp.)*/
   GET_FIELD(cmd_ieee_rx_buf, CMD_IEEE_RX, ccaRssiThr) = 0xA6;
   GET_FIELD(cmd_ieee_rx_buf, CMD_IEEE_RX, numExtEntries) = 0x00;