dm: tegra: cros_ec: Enable Chrome OS EC on Nyan-big

Enable the EC and keyboard, using the SPI bus.

The EC driver requires a particular format and a deactivation delay. Also
U-Boot does not support interrupts.

For now, adjust the device tree to comply. At some point we should tidy
this up to support interrupts and make tegra and exynos use the same setup.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>