gtp-tunnel: display i_tei in help

display <tid|i_tei> in help message that is printed.

Change-Id: I0aa78e654f23a2b6588ac8e1e5508e798caad1a7
diff --git a/tools/gtp-tunnel.c b/tools/gtp-tunnel.c
index 8c8f95f..e8db171 100644
--- a/tools/gtp-tunnel.c
+++ b/tools/gtp-tunnel.c
@@ -133,7 +133,7 @@
 	uint32_t gtp_ifidx;
 
 	if (argc != 6) {
-		printf("%s del <gtp device> <version> <tid> <family>\n",
+		printf("%s del <gtp device> <version> <tid|i_tei> <family>\n",
 			argv[0]);
 		return EXIT_FAILURE;
 	}