manual: Include QoS chapter and add osmo-mgw specific example

Change-Id: I46f632f52a86a50242689a0132a7a7cb2a8feb12
Depends: osmo-gsm-manuals.git Id344c29eda2a9b3e36376302b425e9db1f6c0f28
diff --git a/doc/manuals/osmomgw-usermanual.adoc b/doc/manuals/osmomgw-usermanual.adoc
index c4660f5..7ebc2db 100644
--- a/doc/manuals/osmomgw-usermanual.adoc
+++ b/doc/manuals/osmomgw-usermanual.adoc
@@ -24,6 +24,8 @@
 
 include::./common/chapters/osmux/osmux.adoc[]
 
+include::./common/chapters/qos-dscp-pcp.adoc[]
+
 //include::{srcdir}/chapters/counters.adoc[]
 
 include::./common/chapters/vty_cpu_sched.adoc[]