vty: Introduce cs7-instance-iu

Similar to what we already have in osmo-msc.

Change-Id: Iaa9e1d06dd0430848ef4f7498a3c15d13f899904
diff --git a/doc/examples/osmo-sgsn/osmo-sgsn_custom-sccp.cfg b/doc/examples/osmo-sgsn/osmo-sgsn_custom-sccp.cfg
index a18d76a..f60c076 100644
--- a/doc/examples/osmo-sgsn/osmo-sgsn_custom-sccp.cfg
+++ b/doc/examples/osmo-sgsn/osmo-sgsn_custom-sccp.cfg
@@ -21,6 +21,7 @@
  auth-policy remote
  gsup remote-ip 127.0.0.1
  gsup remote-port 4222
+ cs7-instance-iu 0
 !
 ns
  timer tns-block 3
diff --git a/doc/manuals/vty/sgsn_vty_reference.xml b/doc/manuals/vty/sgsn_vty_reference.xml
index c3f91cf..38e21c2 100644
--- a/doc/manuals/vty/sgsn_vty_reference.xml
+++ b/doc/manuals/vty/sgsn_vty_reference.xml
@@ -2502,6 +2502,12 @@
         <param name='passive' doc='Compression is available on request' />
       </params>
     </command>
+    <command id='cs7-instance-iu &lt;0-15&gt;'>
+      <params>
+        <param name='cs7-instance-iu' doc='Set SS7 to be used by the Iu-Interface.' />
+        <param name='&lt;0-15&gt;' doc='SS7 instance reference number (default: 0)' />
+      </params>
+    </command>
     <command id='iu rab-assign-addr-enc (x213|v4raw)'>
       <params>
         <param name='iu' doc='Iu interface protocol options' />