bsc: Fix compiler warning about wrong return and unused variable

osmo_bsc_api.c: In function ‘bsc_cm_update’:
osmo_bsc_api.c:195:2: warning: ‘return’ with a value, in function returning void [enabled by default]
osmo_bsc_api.c:193:28: warning: unused variable ‘sccp’ [-Wunused-variable]
diff --git a/openbsc/src/osmo-bsc/osmo_bsc_api.c b/openbsc/src/osmo-bsc/osmo_bsc_api.c
index 72e7b9b..db9ceba 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_api.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_api.c
@@ -187,9 +187,8 @@
 			  const uint8_t *cm2, uint8_t cm2_len,
 			  const uint8_t *cm3, uint8_t cm3_len)
 {
-	struct osmo_bsc_sccp_con *sccp;
 	struct msgb *resp;
-	return_when_not_connected_val(conn, 1);
+	return_when_not_connected(conn);
 
 	resp = gsm0808_create_classmark_update(cm2, cm2_len, cm3, cm3_len);