Transceiver: Fix idle ul burst indications being dropped

pullRadioVector() should return true on idle frames because those
indications may be handled by upper layers (TRXDv1). Clarify return code
in function documentation.

Change-Id: If592ed1c04cf7e995f656b313f60edd4d40d1bfd

Transceiver52M/Transceiver.cpp

@@ -587,6 +587,7 @@ void writeToFile(radioVector *radio_burst, size_t chan)
 /*
  * Pull bursts from the FIFO and handle according to the slot
  * and burst correlation type. Equalzation is currently disabled.
+ * returns true on success (bi filled), false on error (bi content undefined).
  */
 bool Transceiver::pullRadioVector(size_t chan, struct trx_ul_burst_ind *bi)
 {
@@ -708,7 +709,7 @@ bool Transceiver::pullRadioVector(size_t chan, struct trx_ul_burst_ind *bi)
 ret_idle:
   bi->idle = true;
   delete radio_burst;
-  return false;
+  return true;
 }
 
 void Transceiver::reset()