deb: fix build by adding libosmogb doc package

Change-Id: I3fe45feaee4033c17e25c4c0552d54a81d9b44f5
Fixes: OS#2340
diff --git a/debian/libosmogb-doc.doc-base b/debian/libosmogb-doc.doc-base
new file mode 100644
index 0000000..f690318
--- /dev/null
+++ b/debian/libosmogb-doc.doc-base
@@ -0,0 +1,7 @@
+Document: libosmogb-doc
+Title: Documentation for the libosmogb library
+Section: Programming
+
+Format: HTML
+Index: /usr/share/doc/libosmocore/gb/html/index.html
+Files: /usr/share/doc/libosmocore/gb/html/*.html