drm/tegra: Shutdown on driver unbind

Since commit 846c7dfc ("drm/atomic: Try to preserve the crtc enabled
state in drm_atomic_remove_fb, v2."), removing the last framebuffer will
no longer disable the corresponding pipeline, which causes the KMS core
to complain about leaked connectors on driver unbind.

Fix this by calling drm_atomic_helper_shutdown() on driver unbind, which
will cause all display pipelines to be shut down and therefore drop the
extra references on the connectors.
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/drm.c

@@ -250,6 +250,7 @@ static void tegra_drm_unload(struct drm_device *drm)
 
 	drm_kms_helper_poll_fini(drm);
 	tegra_drm_fb_exit(drm);
+	drm_atomic_helper_shutdown(drm);
 	drm_mode_config_cleanup(drm);
 
 	err = host1x_device_exit(device);