bsc: Prepare to store the SCCP connection inside the subscriber

openbsc/include/openbsc/gsm_data.h

@@ -4,6 +4,7 @@
 #include <sys/types.h>
 
 struct osmo_msc_data;
+struct osmo_bsc_sccp_con;
 
 enum gsm_phys_chan_config {
 	GSM_PCHAN_NONE,
@@ -243,6 +244,9 @@ struct gsm_subscriber_connection {
 	/* Are we part of a special "silent" call */
 	int silent_call;
 
+	/* bsc structures */
+	struct osmo_bsc_sccp_con *sccp_con;
+
 	/* back pointers */
 	int in_release;
 	struct gsm_lchan *lchan;