ASoC: tegra20: spdif: Improve driver's code

ASoC: tegra20: spdif: Improve driver's code

- Clean up whitespaces, defines and variables.

- Remove obsolete code.

- Adhere to upstream coding style.

- Don't override returned error code.

- Replace pr_err with dev_err.

No functional changes are made by this patch. This is a minor code's
refactoring that will ease further maintenance of the driver.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20211204143725.31646-9-digetx@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>