pinctrl: tegra: init Tegra20/30 at module_init time

The Tegra20/30 pinctrl drivers currently initializes at arch_initcall,
whereas Tegra114/124 pinctrl drivers initialize at module_init time.
Convert Tegra20/30 to work the same way as the other drivers.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>