Transceiver: Update noise level only when the timeslot is marked as IDLE.

We can't rely on an assumption that if we can't decode a burst - it's noise.
There are many rasons why we can't decode a burst even if it's well above the
noise level. Just one example is a RACH burst which can be overlapped with
another RACH burst up to a level both are completely unrecognizable. Another
example is when a burst is destroyed by bad multi-path.

Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
diff --git a/Transceiver52M/Transceiver.h b/Transceiver52M/Transceiver.h
index a7b04ed..45d3980 100644
--- a/Transceiver52M/Transceiver.h
+++ b/Transceiver52M/Transceiver.h
@@ -195,7 +195,7 @@
   void pushRadioVector(GSM::Time &nowTime);
 
   /** Pull and demodulate a burst from the receive FIFO */
-  SoftVector *pullRadioVector(GSM::Time &wTime, double &RSSI,
+  SoftVector *pullRadioVector(GSM::Time &wTime, double &RSSI, bool &isRssiValid,
                               double &timingOffset, double &noise,
                               size_t chan = 0);