sgsn: change configuration to the new NS2

Change the whole vty configuration for NS to be more flexible
and support more setups. Old configurations are invalid.

For further information see:
https://osmocom.org/projects/libosmocore/wiki/Network_service_(NS)

Depends-on: If5bd6b86e130772e6c93d640b0c637985416136d (osmo-sgsn)
Change-Id: I37d010bc4ae553c30feb2ebd2be66d23b96bf42a
diff --git a/sgsn/osmo-sgsn.cfg b/sgsn/osmo-sgsn.cfg
index 7ac50bc..c03c9a3 100644
--- a/sgsn/osmo-sgsn.cfg
+++ b/sgsn/osmo-sgsn.cfg
@@ -47,9 +47,9 @@
  timer tns-test 30
  timer tns-alive 3
  timer tns-alive-retries 10
- encapsulation udp local-ip 127.0.0.10
- encapsulation udp local-port 23000
- encapsulation framerelay-gre enabled 0
+ bind udp local10
+  listen 127.0.0.10 23000
+  accept-ipaccess
 bssgp
 sgsn
  gtp local-ip 127.0.0.10