Fix USRP1 build with support for setting Rx/TxAntenna

The USRP1 build was broken by commit 77ce99ac6720896f504a0581a5c57b2929a13cef.

Commit 77ce99ac6720896f504a0581a5c57b2929a13cef broke the USRP1 build

Change-Id: I28585947d5662cdd580a814cce54a5d9aa30eeb8
diff --git a/Transceiver52M/USRPDevice.h b/Transceiver52M/USRPDevice.h
index f5fbe85..f981643 100644
--- a/Transceiver52M/USRPDevice.h
+++ b/Transceiver52M/USRPDevice.h
@@ -198,6 +198,7 @@
   inline double numberRead() { return samplesRead; }
   inline double numberWritten() { return samplesWritten; }
 
+  std::vector<std::string> tx_paths, rx_paths;
 };
 
 #endif // _USRP_DEVICE_H_