arm64: tegra: Enable native timers on Tegra234

The native timers IP block found on NVIDIA Tegra SoCs implements a
watchdog timer that can be used to recover from system hangs. Add and
enable the device tree node on Tegra234.

Signed-off-by: Kartik <kkartik@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>