gpio: Add Tegra186 support

Tegra186 has two GPIO controllers that are largely register compatible
between one another but are completely different from the controller
found on earlier generations.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>