gpio: tegra: Move driver registration to subsys_init level

There is a bug in regards to deferred probing within the drivers core
that causes GPIO-driver to suspend after its users. The bug appears if
GPIO-driver probe is getting deferred, which happens after introducing
dependency on PINCTRL-driver for the GPIO-driver by defining "gpio-ranges"
property in device-tree. The bug in the drivers core is old (more than 4
years now) and is well known, unfortunately there is no easy fix for it.
The good news is that we can workaround the deferred probe issue by
changing GPIO / PINCTRL drivers registration order and hence by moving
PINCTRL driver registration to the arch_init level and GPIO to the
subsys_init.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>