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/gprs/sgsn_cdr.c b/openbsc/src/gprs/sgsn_cdr.c
index bf0d6f7..0910896 100644
--- a/openbsc/src/gprs/sgsn_cdr.c
+++ b/openbsc/src/gprs/sgsn_cdr.c
@@ -227,8 +227,8 @@
 		clock_gettime(CLOCK_MONOTONIC, &signal_data->pdp->cdr_start);
 		signal_data->pdp->cdr_charging_id = signal_data->pdp->lib->cid;
 		cdr_log_pdp(inst, "pdp-act", signal_data->pdp);
-		signal_data->pdp->cdr_timer.cb = cdr_pdp_timeout;
-		signal_data->pdp->cdr_timer.data = signal_data->pdp;
+		osmo_timer_setup(&signal_data->pdp->cdr_timer, cdr_pdp_timeout,
+				 signal_data->pdp);
 		osmo_timer_schedule(&signal_data->pdp->cdr_timer, inst->cfg.cdr.interval, 0);
 		break;
 	case S_SGSN_PDP_DEACT: