Reverting a change introduced in 6de7e7f8b3698 "[drm] upstream sync to v4.10"
(upstream c470abd4fde40ea).

Index: src/drivers/gpu/drm/mgag200/mgag200_ttm.c
===================================================================
--- src.orig/drivers/gpu/drm/mgag200/mgag200_ttm.c	2017-06-20 20:40:34.664915876 +0200
+++ src/drivers/gpu/drm/mgag200/mgag200_ttm.c	2017-06-20 20:40:45.435756224 +0200
@@ -150,8 +150,7 @@
 {
 	struct mgag200_bo *mgabo = mgag200_bo(bo);
 
-	return drm_vma_node_verify_access(&mgabo->gem.vma_node,
-					  filp->private_data);
+	return drm_vma_node_verify_access(&mgabo->gem.vma_node, filp);
 }
 
 static int mgag200_ttm_io_mem_reserve(struct ttm_bo_device *bdev,