merge simtrace2-discovery.[ch] to libusb_util.[ch]

Change-Id: I4defbec70986a90c1f0cfb7587393265b73c0163
diff --git a/host/src/usb2udp.c b/host/src/usb2udp.c
index 9927594..23800fd 100644
--- a/host/src/usb2udp.c
+++ b/host/src/usb2udp.c
@@ -37,7 +37,7 @@
 
 #include <osmocom/simtrace2/simtrace_usb.h>
 #include <osmocom/simtrace2/simtrace_prot.h>
-#include "simtrace2-discovery.h"
+#include <osmocom/simtrace2/libusb_util.h>
 
 #include <osmocom/core/utils.h>
 #include <osmocom/core/socket.h>