[otbn] Add missing output port

We don't use this port, but VCS complains about an incomplete port list.

Signed-off-by: Philipp Wagner <phw@lowrisc.org>
diff --git a/hw/ip/otbn/dv/uvm/tb.sv b/hw/ip/otbn/dv/uvm/tb.sv
index 896d9c1..1d536dc 100644
--- a/hw/ip/otbn/dv/uvm/tb.sv
+++ b/hw/ip/otbn/dv/uvm/tb.sv
@@ -176,6 +176,9 @@
 
     .start_i      (model_if.start),
     .done_o       (model_if.done),
+
+    .err_bits_o   (),
+
     .start_addr_i (model_if.start_addr),
 
     .edn_rnd_data_valid_i  (edn_rnd_data_valid),