lms: Fail in case of unsupported configuration

There might be some configuration that's not supported by osmo-bts-lms,
and we should reject that properly.

Change-Id: I6f82edce589030a4407f6150fb7e8abe6417c1f2
Closes: OS#3347
diff --git a/Transceiver52M/device/lms/LMSDevice.cpp b/Transceiver52M/device/lms/LMSDevice.cpp
index 815a4c5..16585e6 100644
--- a/Transceiver52M/device/lms/LMSDevice.cpp
+++ b/Transceiver52M/device/lms/LMSDevice.cpp
@@ -625,5 +625,13 @@
 			       const std::vector < std::string > &tx_paths,
 			       const std::vector < std::string > &rx_paths)
 {
+	if (tx_sps != rx_sps) {
+		LOG(ERROR) << "LMS Requires tx_sps == rx_sps";
+		return NULL;
+	}
+	if (lo_offset != 0.0) {
+		LOG(ERROR) << "LMS doesn't support lo_offset";
+		return NULL;
+	}
 	return new LMSDevice(tx_sps, rx_sps, iface, chans, lo_offset, tx_paths, rx_paths);
 }