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/libbsc/paging.c b/openbsc/src/libbsc/paging.c
index 324104f..2dcd3b4 100644
--- a/openbsc/src/libbsc/paging.c
+++ b/openbsc/src/libbsc/paging.c
@@ -262,7 +262,7 @@
 		req, req->subscr->imsi);
 
 	/* must be destroyed before calling cbfn, to prevent double free */
-	counter_inc(req->bts->network->stats.paging.expired);
+	osmo_counter_inc(req->bts->network->stats.paging.expired);
 	cbfn_param = req->cbfn_param;
 	cbfn = req->cbfn;
 
@@ -311,7 +311,7 @@
 	struct gsm_bts *bts = NULL;
 	int num_pages = 0;
 
-	counter_inc(network->stats.paging.attempted);
+	osmo_counter_inc(network->stats.paging.attempted);
 
 	/* start paging subscriber on all BTS within Location Area */
 	do {
@@ -337,7 +337,7 @@
 	} while (1);
 
 	if (num_pages == 0)
-		counter_inc(network->stats.paging.detached);
+		osmo_counter_inc(network->stats.paging.detached);
 
 	return num_pages;
 }