gprs_ns2: introduce gprs_ns2_vty_init_reduced() for the PCU

The gprs_ns2_vty_init_reduced() call initialized the ns2 vty without
configuration nodes (except timeout). The PCU can be only configured
by the BTS/BSC. It should not configured by vty.

Change-Id: I4437da74bd48ba64d3f16ea67afc26c45b6d3ac9
diff --git a/src/gb/libosmogb.map b/src/gb/libosmogb.map
index 71be117..a3171d0 100644
--- a/src/gb/libosmogb.map
+++ b/src/gb/libosmogb.map
@@ -185,6 +185,7 @@
 gprs_ns2_sns_add_endpoint;
 gprs_ns2_sns_del_endpoint;
 gprs_ns2_vty_init;
+gprs_ns2_vty_init_reduced;
 
 gprs_nsvc_create2;
 gprs_nsvc_delete;