arm64: tegra: Add NVIDIA P2530 main board support

The NVIDIA P2530 is a processor module used in several reference designs
that features a Tegra210 SoC, 4 GiB of LPDDR4 RAM, 16 GiB eMMC and other
essentials. It is typically connected to some I/O board that provides
the connectors needed to hook it up to the outside world.

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