src: use namespace prefix osmo_counter*

Summary of changes:

s/struct counter/struct osmo_counter/g
s/counter_inc/osmo_counter_inc/g
s/counter_get/osmo_counter_get/g
s/counter_reset/osmo_counter_reset/g
s/counter_alloc/osmo_counter_alloc/g
s/counter_free/osmo_counter_free
diff --git a/openbsc/src/osmo-bsc_nat/bsc_sccp.c b/openbsc/src/osmo-bsc_nat/bsc_sccp.c
index f7d868a..de6b421 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_sccp.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_sccp.c
@@ -129,7 +129,7 @@
 	bsc_mgcp_init(conn);
 	llist_add_tail(&conn->list_entry, &bsc->nat->sccp_connections);
 	rate_ctr_inc(&bsc->cfg->stats.ctrg->ctr[BCFG_CTR_SCCP_CONN]);
-	counter_inc(bsc->cfg->nat->stats.sccp.conn);
+	osmo_counter_inc(bsc->cfg->nat->stats.sccp.conn);
 
 	LOGP(DNAT, LOGL_DEBUG, "Created 0x%x <-> 0x%x mapping for con %p\n",
 	     sccp_src_ref_to_int(&conn->real_ref),