Transceiver52M: Set variable thread priority levels

The transceiver and underlying device drivers are threaded. use
the following priority levels.

0.50 - UHD driver internal threads
0.45 - Receive device drive thread
0.44 - Transmit device drive thread
0.43 - UHD asynchronous update thread (error reporting)
0.42 - Receive burst processing thread(s)

Signed-off-by: Thomas Tsou <tom@tsou.cc>
diff --git a/Transceiver52M/radioDevice.h b/Transceiver52M/radioDevice.h
index e577bc5..19b5a88 100644
--- a/Transceiver52M/radioDevice.h
+++ b/Transceiver52M/radioDevice.h
@@ -52,7 +52,7 @@
   virtual enum TxWindowType getWindowType()=0;
 
   /** Enable thread priority */
-  virtual void setPriority()=0;
+  virtual void setPriority(float prio = 0.5) = 0;
 
   /**
 	Read samples from the radio.