debian: remove doublicated project name in example files

For example:
/usr/share/doc/osmo-sgsn/examples/osmo-sgsn/osmo-sgsn.cfg -> /usr/share/doc/osmo-sgsn/examples/osmo-sgsn.cfg

Change-Id: I77f9665e78e3e55910efb30cb50cefdb138e19f7
diff --git a/debian/osmo-sgsn.install b/debian/osmo-sgsn.install
index bde329a..9390deb 100644
--- a/debian/osmo-sgsn.install
+++ b/debian/osmo-sgsn.install
@@ -1,2 +1,3 @@
 usr/bin/osmo-sgsn
-usr/share/doc/osmo-sgsn/examples/osmo-sgsn
+usr/share/doc/osmo-sgsn/examples/osmo-sgsn/osmo-sgsn.cfg usr/share/doc/osmo-sgsn/examples
+usr/share/doc/osmo-sgsn/examples/osmo-sgsn/osmo-sgsn-accept-all.cfg usr/share/doc/osmo-sgsn/examples