i2c: tegra: Clean up probe function

The driver's probe function code is a bit difficult to read. This patch
reorders code of the probe function, forming groups of code that are easy
to work with. The probe tear-down order now matches the driver-removal
order.

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>