gpio: tegra186: Add HTE support

Tegra194 AON GPIO controller with the use of its internal hardware
timestamping engine (HTE), also known as GTE, can timestamp GPIO lines
through system counter. This patch implements enable/disable callbacks
for the GPIO controller. In enable call, it will set timestamp function
bit and GPIO line rising/falling edges in the config register. In
disable call, it restores the state.

Signed-off-by: Dipen Patel <dipenp@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>