doc: Include mgwpool.adoc from osmo-gsm-manuals

This way we document the recently gained support for MGW pooling.

Related: SYS#5987
Depends: osmo-gsm-manuals.git Change-Id Ieda0d4bfe6fc90da6e19c791d8ec2da89427ba3b
Change-Id: I9d8116a74a63591599c4cbafa60f9a313e6ab19c
diff --git a/doc/manuals/osmomsc-usermanual.adoc b/doc/manuals/osmomsc-usermanual.adoc
index 7ba45d4..632abc7 100644
--- a/doc/manuals/osmomsc-usermanual.adoc
+++ b/doc/manuals/osmomsc-usermanual.adoc
@@ -32,6 +32,8 @@
 
 include::{srcdir}/chapters/osmux_msc.adoc[]
 
+include::./common/chapters/mgwpool.adoc[]
+
 include::./common/chapters/control_if.adoc[]
 
 include::./common/chapters/gsup.adoc[]