debian: Package installed example doc files

Change-Id: I71afa4799e0b484879b96567acd004755a84027f
diff --git a/debian/osmo-bsc-mgcp.install b/debian/osmo-bsc-mgcp.install
index 1550437..bed2f47 100644
--- a/debian/osmo-bsc-mgcp.install
+++ b/debian/osmo-bsc-mgcp.install
@@ -1 +1,2 @@
 usr/bin/osmo-bsc_mgcp
+usr/share/doc/osmo-mgw/examples/osmo-bsc_mgcp/mgcp.cfg