drm/vgem: Switch to reservation_object_lock() helpers

For the convenience of encapsulation the reservation object's ww_mutex
was wrapped in pair of lock/unlock helpers.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170123095357.29514-1-chris@chris-wilson.co.uk

drivers/gpu/drm/vgem/vgem_fence.c

@@ -190,12 +190,12 @@ int vgem_fence_attach_ioctl(struct drm_device *dev,
 
 	/* Expose the fence via the dma-buf */
 	ret = 0;
-	ww_mutex_lock(&resv->lock, NULL);
+	reservation_object_lock(resv, NULL);
 	if (arg->flags & VGEM_FENCE_WRITE)
 		reservation_object_add_excl_fence(resv, fence);
 	else if ((ret = reservation_object_reserve_shared(resv)) == 0)
 		reservation_object_add_shared_fence(resv, fence);
-	ww_mutex_unlock(&resv->lock);
+	reservation_object_unlock(resv);
 
 	/* Record the fence in our idr for later signaling */
 	if (ret == 0) {