Tweak BasebandConfiguration constructors to avoid surprise type conversions.

firmware/application/receiver_model.cpp

@@ -126,11 +126,7 @@ void ReceiverModel::enable() {
 void ReceiverModel::disable() {
 	/* TODO: This is a dumb hack to stop baseband from working so hard. */
 	BasebandConfigurationMessage message {
-		.configuration = {
-			.mode = -1,
-			.sampling_rate = 0,
-			.decimation_factor = 1,
-		}
+		.configuration = { },
 	};
 	shared_memory.baseband_queue.push(message);