drm/tegra: plane: Implement zpos plane property for older Tegras

Older Tegra's do not support plane's Z position handling in hardware,
but the hardware provides knobs to implement it in software.

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