drm/i915: drop duplicate ggtt vma list add in setup_global_gtt

Preallocated objects will already have been added to the vma_list when
creating their ggtt vma entry, and coincidentally also marked as holding
a ggtt mapping. Repeating the vma_list manipulation when setting up the
ggtt after preallocation is a recipe for an unhappy kernel.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: Use the improve commit message suggest by Chris.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -759,7 +759,6 @@ void i915_gem_setup_global_gtt(struct drm_device *dev,
 		if (ret)
 			DRM_DEBUG_KMS("Reservation failed\n");
 		obj->has_global_gtt_mapping = 1;
-		list_add(&vma->vma_link, &obj->vma_list);
 	}
 
 	dev_priv->gtt.base.start = start;