src: use osmo_timer_setup()

Use new function available in libosmocore to set up timers. Compile
tested only.

Change-Id: Ibcfd915688e97d370a888888a83a7c95cbe16819
diff --git a/openbsc/src/libmgcp/mgcp_protocol.c b/openbsc/src/libmgcp/mgcp_protocol.c
index 18398fc..4fcadd9 100644
--- a/openbsc/src/libmgcp/mgcp_protocol.c
+++ b/openbsc/src/libmgcp/mgcp_protocol.c
@@ -1172,8 +1172,7 @@
 void mgcp_trunk_set_keepalive(struct mgcp_trunk_config *tcfg, int interval)
 {
 	tcfg->keepalive_interval = interval;
-	tcfg->keepalive_timer.data = tcfg;
-	tcfg->keepalive_timer.cb = mgcp_keepalive_timer_cb;
+	osmo_timer_setup(&tcfg->keepalive_timer, mgcp_keepalive_timer_cb, tcfg);
 
 	if (interval <= 0)
 		osmo_timer_del(&tcfg->keepalive_timer);