Test "device_tree_model_not_empty" failed on TI Panda and ARM Versatile Express A9 ubuntu.

On Linux Linaro daily test dashboard, test "device_tree_model_not_empty" failed on TI Panda 4430, 4460 and ARM Versatile Express A9 images. The error information is same:

+ test_device_tree_model_not_empty
+ TEST=device_tree_model_not_empty
+ '[' '!' -f /proc/device-tree/model ']'
+ fail_test 'Unable to find /proc/device-tree/model'
+ local 'reason=Unable to find /proc/device-tree/model'
+ echo 'device_tree_model_not_empty: FAIL - Unable to find /proc/device-tree/model'
device_tree_model_not_empty: FAIL - Unable to find /proc/device-tree/model
+ return 1

It happened since build 297.