soc/tegra: Add Tegra210 support

Also known as Tegra X1, the Tegra210 has four Cortex-A57 cores paired
with four Cortex-A53 cores in a switched configuration. It features a
GPU using the Maxwell architecture with support for DX11, SM4, OpenGL
4.5, OpenGL ES 3.1 and providing 256 CUDA cores. It supports hardware
accelerated en- and decoding of various video standards including
H.265, H.264 and VP8 at 4K resolutions and up to 60 fps.

Besides the multimedia features it also comes with a variety of I/O
controllers such as GPIO, I2C, SPI, SDHCI, PCIe, SATA and XHCI, to
name only a few.

Add a Kconfig option for Tegra210 to allow SoC-specific support to be
enabled for this new generation.

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