drm/i915: Remove redundant deletion of obj->gpu_write_list

At that point as the object is no longer in any GPU write domain it must
not be on the list, so the list_del() is redundant.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_gem.c

@@ -3857,8 +3857,6 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 		if (obj->write_domain)
 			list_move_tail(&obj_priv->gpu_write_list,
 				       &dev_priv->mm.gpu_write_list);
-		else
-			list_del_init(&obj_priv->gpu_write_list);
 
 		trace_i915_gem_object_change_domain(obj,
 						    obj->read_domains,