ARM: tegra: nyan: Add gpio-restart node

The Nyan Chromebooks have a GPIO line dedicated to restarting the
system. Using this line will make sure that the TPM is restarted as
well.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>