[CORD-2810] Only synchronizers can write feedback state

Change-Id: Ia3f28763a0212a570186e4c6c5cb118c40325b5b
diff --git a/lib/xos-genx/xosgenx/targets/modeldefs.xtarget b/lib/xos-genx/xosgenx/targets/modeldefs.xtarget
index 3b0790a..15c43d7 100644
--- a/lib/xos-genx/xosgenx/targets/modeldefs.xtarget
+++ b/lib/xos-genx/xosgenx/targets/modeldefs.xtarget
@@ -29,6 +29,7 @@
     {% endfor %}
   {%- endif %}
     type: {{ xproto_type_to_ui_type(f) }}
+    read_only: {{ xproto_is_true(f.options.feedback_state) }}
     {% set validators = xproto_validators(f) -%}
     {% if validators -%}
     validators: