drm/tegra: gr3d: Properly clean up resources

Failure to register the Tegra DRM client would leak the resources. Move
cleanup code to error unwinding gotos to fix that and share the cleanup
code with the other error paths.

Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>