radioInterfaceMulti: Override setTxGain() to avoid chan!=0 calls

Change-Id: I7e67f660c3b0b009db59b405de603f6058021802
diff --git a/Transceiver52M/radioInterfaceMulti.cpp b/Transceiver52M/radioInterfaceMulti.cpp
index c41ec22..4022d3a 100644
--- a/Transceiver52M/radioInterfaceMulti.cpp
+++ b/Transceiver52M/radioInterfaceMulti.cpp
@@ -405,3 +405,12 @@
   else
     return mDevice->getRxGain();
 }
+
+double RadioInterfaceMulti::setTxGain(double dB, size_t chan)
+{
+	if (chan == 0)
+		return mDevice->setTxGain(dB);
+	else
+		return mDevice->getTxGain();
+
+}