gpio: tegra186: Implement wake event support

gpio: tegra186: Implement wake event support

The GPIO controller doesn't have any controls to enable the system to
wake up from low power states based on activity on GPIO pins. An extra
hardware block that is part of the power management controller (PMC)
contains these controls. In order for the GPIO controller to be able
to cooperate with the PMC, obtain a reference to the PMC's IRQ domain
and make it a parent to the GPIO controller's IRQ domain. This way the
PMC gets an opportunity to program the additional registers required
to enable wakeup sources on suspend.

Based on additional work by Bitan Biswas <bbiswas@nvidia.com>.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20191002144502.156393-2-thierry.reding@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>