examples: Add secondary ipv6 google DNS to osmo-ggsn.cfg

Change-Id: I5efbd1848a7974cb8dc614c4567de2658b9a7269
diff --git a/doc/examples/osmo-ggsn.cfg b/doc/examples/osmo-ggsn.cfg
index 763e561..8317684 100644
--- a/doc/examples/osmo-ggsn.cfg
+++ b/doc/examples/osmo-ggsn.cfg
@@ -53,6 +53,7 @@
   type-support v6
   ipv6 prefix dynamic 2001:780:44:2000:0:0:0:0/56
   ipv6 dns 0 2001:4860:4860::8888
+  ipv6 dns 1 2001:4860:4860::8844
   ipv6 ifconfig 2001:780:44:2000:0:0:0:0/56
   no shutdown
  apn inet46
@@ -65,6 +66,7 @@
   ip ifconfig 176.16.46.0/24
   ipv6 prefix dynamic 2001:780:44:2100:0:0:0:0/56
   ipv6 dns 0 2001:4860:4860::8888
+  ipv6 dns 1 2001:4860:4860::8844
   ipv6 ifconfig 2001:780:44:2100:0:0:0:0/56
   no shutdown
  default-apn internet