drm: Initialize object type when using DRM_MODE() macro

DRM_MODE() macro doesn't initialize the type of the base drm object.
When a copy is made of the mode, the object type is overwritten with
zero, and the the object can no longer be found by
drm_mode_object_find() due to the type check failing.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>