drm/i915: s/obj->exec_list/obj->obj_exec_link in debugfs

To convert the execbuf code over to use vmas natively we need to
shuffle the exec_list a bit. This patch here just prepares things with
the debugfs code, which also uses the old exec_list list_head, newly
called obj_exec_link.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
[danvet: Split out from Ben's big patch.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 41dc042..ce40e27 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3992,6 +3992,7 @@
 	INIT_LIST_HEAD(&obj->global_list);
 	INIT_LIST_HEAD(&obj->ring_list);
 	INIT_LIST_HEAD(&obj->exec_list);
+	INIT_LIST_HEAD(&obj->obj_exec_link);
 	INIT_LIST_HEAD(&obj->vma_list);
 
 	obj->ops = ops;