arm64: tegra: Add support for Google Pixel C

Add initial device-tree support for Google Pixel C (a.k.a. Smaug) based
upon Tegra210 SoC with 3 GiB of LPDDR4 RAM.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Andrew Bresticker <abrestic@chromium.org>
Tested-by: Andrew Bresticker <abrestic@chromium.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>