drm/tegra: Fix ordering of cleanup code

Commit Fixes: b9f8b09c ("drm/tegra: Setup shared IOMMU domain after
initialization") changed the initialization order of the IOMMU related
bits but didn't update the cleanup path accordingly. This asymmetry can
cause failures during error recovery.

Fixes: b9f8b09c

 ("drm/tegra: Setup shared IOMMU domain after initialization")
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>