user_simtrace2: Stop using printf, use libosmocore logging

This way we have consistent logging from all parts of the code via
the common libosmocore logging infrastructure.

Change-Id: I9ace31d781dd3e50f9a5d9239bafa87a01abb0d6
diff --git a/src/debug.h b/src/debug.h
index e3994b4..2a3e5a3 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -3,6 +3,7 @@
 
 enum {
 	DMAIN,
+	DST2,
 };
 
 extern const struct log_info log_info;