drm/tegra: Allow VBLANK to be disabled

Signed-off-by: Thierry Reding <treding@nvidia.com>
diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index 427f50c..497b4a0 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -182,6 +182,7 @@
 
 	/* syncpoints are used for full 32-bit hardware VBLANK counters */
 	drm->max_vblank_count = 0xffffffff;
+	drm->vblank_disable_allowed = true;
 
 	err = drm_vblank_init(drm, drm->mode_config.num_crtc);
 	if (err < 0)