gprs: Document the stale option in delete-gbproxy-tlli
diff --git a/openbsc/src/gprs/gb_proxy_vty.c b/openbsc/src/gprs/gb_proxy_vty.c
index f1811c3..dcdc06c 100644
--- a/openbsc/src/gprs/gb_proxy_vty.c
+++ b/openbsc/src/gprs/gb_proxy_vty.c
@@ -508,6 +508,7 @@
 	"NSEI number\n"
 	"Delete entries with a matching TLLI (hex)\n"
 	"Delete entries with a matching IMSI\n"
+	"Delete stale entries\n"
 	"Identification to match\n")
 {
 	const uint16_t nsei = atoi(argv[0]);