ttm: Make parts of a struct ttm_bo_device global.

Common resources, like memory accounting and swap lists should be
global and not per device. Introduce a struct ttm_bo_global to
accomodate this, and register it with sysfs. Add a small sysfs interface
to return the number of active buffer objects.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@linux.ie>

include/drm/ttm/ttm_bo_api.h

@@ -155,6 +155,7 @@ struct ttm_buffer_object {
 	 * Members constant at init.
 	 */
 
+	struct ttm_bo_global *glob;
 	struct ttm_bo_device *bdev;
 	unsigned long buffer_start;
 	enum ttm_bo_type type;