drm/tegra: hub: Use state directly

Using drm_atomic_get_private_obj_state() after state has been swapped
will return old state.

Fixes: 0281c414 ("drm/tegra: hub: Use private object for global state")
Signed-off-by: Stefan Schake <stschake@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>