ASoC: tegra20: spdif: Support device-tree

Tegra20 S/PDIF driver was added in a pre-DT era and was never used since
that time. Revive driver by adding device-tree support.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20211204143725.31646-8-digetx@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>