i2c: tegra: Clean up and improve comments

Make all comments to be consistent in regards to capitalization and
punctuation, correct spelling and grammar errors, improve wording.

Reviewed-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>