libctrl: Change controlif_setup so it returns the ctrl handle

nat: Catch up with controlif_setup API change
We now save a control handle reference in the nat
osmo-bsc: Catch up with controlif_setup API change
We now save a control handle reference in the gsm network
diff --git a/openbsc/include/openbsc/gsm_data.h b/openbsc/include/openbsc/gsm_data.h
index 572f8f5..dea4119 100644
--- a/openbsc/include/openbsc/gsm_data.h
+++ b/openbsc/include/openbsc/gsm_data.h
@@ -266,6 +266,9 @@
 	/* subscriber related features */
 	int keep_subscr;
 	struct gsm_sms_queue *sms_queue;
+
+	/* control interface */
+	struct ctrl_handle *ctrl;
 };
 
 #define SMS_HDR_SIZE	128