Use new stat item/ctr getter APIs

Generated with spatch:
"""
@@
expression E1, E2;
@@
- &E2->ctr[E1]
+ rate_ctr_group_get_ctr(E2, E1)
"""

"""
@@
expression E1, E2, E3;
@@
- E2->items[E1]
+ osmo_stat_item_group_get_item(E2, E1)
"""

Change-Id: I41297a8df68e28dfc6016330ac82b0ed5dd0ebc1
diff --git a/src/gb/gprs_ns2_fr.c b/src/gb/gprs_ns2_fr.c
index 84f3784..7791094 100644
--- a/src/gb/gprs_ns2_fr.c
+++ b/src/gb/gprs_ns2_fr.c
@@ -347,7 +347,7 @@
 {
 	struct priv_bind *priv = bind->priv;
 	llist_add(&msg->list, &priv->backlog.list);
-	osmo_stat_item_inc(bind->statg->items[NS2_BIND_STAT_BACKLOG_LEN], 1);
+	osmo_stat_item_inc(osmo_stat_item_group_get_item(bind->statg, NS2_BIND_STAT_BACKLOG_LEN), 1);
 	osmo_timer_schedule(&priv->backlog.timer, 0, priv->backlog.retry_us);
 }
 
@@ -355,7 +355,7 @@
 {
 	struct priv_bind *priv = bind->priv;
 	llist_add_tail(&msg->list, &priv->backlog.list);
-	osmo_stat_item_inc(bind->statg->items[NS2_BIND_STAT_BACKLOG_LEN], 1);
+	osmo_stat_item_inc(osmo_stat_item_group_get_item(bind->statg, NS2_BIND_STAT_BACKLOG_LEN), 1);
 	osmo_timer_schedule(&priv->backlog.timer, 0, priv->backlog.retry_us);
 }
 
@@ -439,7 +439,7 @@
 			llist_add(&msg->list, &priv->backlog.list);
 			break;
 		}
-		osmo_stat_item_dec(bind->statg->items[NS2_BIND_STAT_BACKLOG_LEN], 1);
+		osmo_stat_item_dec(osmo_stat_item_group_get_item(bind->statg, NS2_BIND_STAT_BACKLOG_LEN), 1);
 	}
 
 restart_timer: