it should be defined as "device_type: {{device_type}}" in the root master.jinja2 files

[liuyq]

to avoid defining the device_type block like the following everywhere:
{% block device_type %}dragonboard-410c{% endblock %}

The prerequisite is that the device file name must be the same as the device type name defined by the lava instance.

[liuyq]

change submitted here: #184