Use new stat item/ctr getter APIs

Patch mostly done with the help of several small spatch snippets.

Change-Id: I600c7a8725f5b229b1a2feb879da7c3b2dce4505
diff --git a/src/gprs_bssgp_pcu.c b/src/gprs_bssgp_pcu.c
index 7ee2e45..0e8e145 100644
--- a/src/gprs_bssgp_pcu.c
+++ b/src/gprs_bssgp_pcu.c
@@ -538,8 +538,8 @@
 	if (bctx)
 	{
 		log_set_context(LOG_CTX_GB_BVC, bctx);
-		rate_ctr_inc(&bctx->ctrg->ctr[BSSGP_CTR_PKTS_IN]);
-		rate_ctr_add(&bctx->ctrg->ctr[BSSGP_CTR_BYTES_IN], msgb_bssgp_len(msg));
+		rate_ctr_inc(rate_ctr_group_get_ctr(bctx->ctrg, BSSGP_CTR_PKTS_IN));
+		rate_ctr_add(rate_ctr_group_get_ctr(bctx->ctrg, BSSGP_CTR_BYTES_IN), msgb_bssgp_len(msg));
 	}
 
 	if (ns_bvci == BVCI_SIGNALLING)