backend-drm: do not print head info twice
Before this patch, when a new head is found its information is printed first as "updated" and then as "found" in the log.
The reason is that drm_head_create()
calls drm_head_update_info()
which
printed the head as "changed". Then drm_head_create()
itself prints it
as "found".
This fixes it to print only once as "found".