make register button text visible in extra small displays

devapp/templates/devapp/dev.html

@@ -72,7 +72,7 @@
                 {% endif %}
                 {% if perms.devapp.change_device %}
                     <a href="{% url 'devapp:dev_register' grp_id dev.pk %}" class="btn btn-default btn-cmd">
-                        <span class="glyphicon glyphicon-fire"></span> <span class="hidden-xs">{% trans 'Register device' %}</span>
+                        <span class="glyphicon glyphicon-fire"></span> {% trans 'Register device' %}
                     </a>
                     <a href="{% url 'devapp:extra_data_edit' grp_id dev.pk %}" class="btn btn-default btn-modal">
                         <span class="glyphicon glyphicon-cog"></span> <span class="hidden-xs">{% trans 'Tech date' %}</span>