src: use namespace prefix osmo_wqueue*

Summary of changes:

s/struct write_queue/struct osmo_wqueue/g
s/write_queue_init/osmo_wqueue_init/g
s/write_queue_clear/osmo_wqueue_clear/g
s/write_queue_enqueue/osmo_wqueue_enqueue/g
s/write_queue_bfd_cb/osmo_wqueue_bfd_cb/g
diff --git a/openbsc/src/osmo-bsc_nat/bsc_ussd.c b/openbsc/src/osmo-bsc_nat/bsc_ussd.c
index 910ef40..69cb7a4 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_ussd.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_ussd.c
@@ -60,7 +60,7 @@
 	close(con->queue.bfd.fd);
 	osmo_fd_unregister(&con->queue.bfd);
 	osmo_timer_del(&con->auth_timeout);
-	write_queue_clear(&con->queue);
+	osmo_wqueue_clear(&con->queue);
 	talloc_free(con);
 }
 
@@ -218,7 +218,7 @@
 		return -1;
 	}
 
-	write_queue_init(&conn->queue, 10);
+	osmo_wqueue_init(&conn->queue, 10);
 	conn->queue.bfd.data = conn;
 	conn->queue.bfd.fd = fd;
 	conn->queue.bfd.when = BSC_FD_READ;