drm/nouveau: stop using persistent_swap_storage

According to Ben this is most likely just a leftover.
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/391078/?series=81804&rev=1Reviewed-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/nouveau/nouveau_gem.c

@@ -209,7 +209,6 @@ nouveau_gem_new(struct nouveau_cli *cli, u64 size, int align, uint32_t domain,
 	if (drm->client.device.info.family >= NV_DEVICE_INFO_V0_TESLA)
 		nvbo->valid_domains &= domain;
 
-	nvbo->bo.persistent_swap_storage = nvbo->bo.base.filp;
 	*pnvbo = nvbo;
 	return 0;
 }