drm/logicvc: Fix device node reference leak in logicvc_drm_config_parse()

In the Linux kernel, the following vulnerability has been resolved:

drm/logicvc: Fix device node reference leak in logicvc_drm_config_parse()

The logicvc_drm_config_parse() function calls of_get_child_by_name() to

find the "layers" node but fails to release the reference, leading to a

device node reference leak.

Fix this by using the __free(device_node) cleanup attribute to automatic

release the reference when the variable goes out of scope.