example config: use RFC1918 addresses for GGSN pools

It's 172.16, not 176.16.

Change-Id: I2d83ee747e8987f10c4960d42f3c3f2a723e3f4c
diff --git a/doc/examples/osmo-ggsn.cfg b/doc/examples/osmo-ggsn.cfg
index e79fdfa..02523e9 100644
--- a/doc/examples/osmo-ggsn.cfg
+++ b/doc/examples/osmo-ggsn.cfg
@@ -42,10 +42,10 @@
   gtpu-mode tun
   tun-device tun4
   type-support v4
-  ip prefix dynamic 176.16.222.0/24
+  ip prefix dynamic 172.16.222.0/24
   ip dns 0 8.8.8.8
   ip dns 1 8.8.4.4
-  ip ifconfig 176.16.222.0/24
+  ip ifconfig 172.16.222.0/24
   no shutdown
  apn inet6
   gtpu-mode tun
@@ -60,10 +60,10 @@
   gtpu-mode tun
   tun-device tun46
   type-support v4v6
-  ip prefix dynamic 176.16.46.0/24
+  ip prefix dynamic 172.16.46.0/24
   ip dns 0 8.8.8.8
   ip dns 1 8.8.4.4
-  ip ifconfig 176.16.46.0/24
+  ip ifconfig 172.16.46.0/24
   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