drm: add _DRM_DRIVER flag, and re-order unload.

Allow drivers to addmaps that won't be removed by lastclose or unload.
The unload needs to be re-ordered to avoid removing the hashs before
the driver has removed the final maps.

Signed-off-by: Dave Airlie <airlied@linux.ie>
diff --git a/drivers/char/drm/drm.h b/drivers/char/drm/drm.h
index 82fb3d0..3a05c6d 100644
--- a/drivers/char/drm/drm.h
+++ b/drivers/char/drm/drm.h
@@ -202,7 +202,8 @@
 	_DRM_KERNEL = 0x08,	     /**< kernel requires access */
 	_DRM_WRITE_COMBINING = 0x10, /**< use write-combining if available */
 	_DRM_CONTAINS_LOCK = 0x20,   /**< SHM page that contains lock */
-	_DRM_REMOVABLE = 0x40	     /**< Removable mapping */
+	_DRM_REMOVABLE = 0x40,	     /**< Removable mapping */
+	_DRM_DRIVER = 0x80	     /**< Managed by driver */
 };
 
 struct drm_ctx_priv_map {