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_nat.c b/openbsc/src/osmo-bsc_nat/bsc_nat.c
index f732488..5df4cd8 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat.c
@@ -663,7 +663,7 @@
 		case SCCP_MSG_TYPE_IT:
 			con = patch_sccp_src_ref_to_bsc(msg, parsed, nat);
 			if (parsed->gsm_type == BSS_MAP_MSG_ASSIGMENT_RQST) {
-				counter_inc(nat->stats.sccp.calls);
+				osmo_counter_inc(nat->stats.sccp.calls);
 
 				if (con) {
 					struct rate_ctr_group *ctrg;
@@ -752,7 +752,7 @@
 
 static void msc_connection_connected(struct bsc_msc_connection *con)
 {
-	counter_inc(nat->stats.msc.reconn);
+	osmo_counter_inc(nat->stats.msc.reconn);
 }
 
 static void msc_send_reset(struct bsc_msc_connection *msc_con)
@@ -1211,7 +1211,7 @@
 	}
 
 	/* count the reconnect */
-	counter_inc(nat->stats.bsc.reconn);
+	osmo_counter_inc(nat->stats.bsc.reconn);
 
 	/*
 	 * if we are not connected to a msc... just close the socket