Back RUA/RANAP integration until RANAP Reset works for cs+ps

The hNodeB is now actively transmitting and we are getting up to the
HNBAP UE-REGISTER.req with the IMSI of the MS.
diff --git a/src/hnbgw_rua.h b/src/hnbgw_rua.h
index 97c35f0..69b2382 100644
--- a/src/hnbgw_rua.h
+++ b/src/hnbgw_rua.h
@@ -4,3 +4,5 @@
 
 int hnbgw_rua_rx(struct hnb_context *hnb, struct msgb *msg);
 int hnbgw_rua_init(void);
+
+int rua_tx_udt(struct msgb *inmsg);