tegra: fdt: Add Tegra2x device tree file from kernel

This was taken from commit b48c54e2 at:
git://git.kernel.org/pub/scm/linux/kernel/git/olof/tegra.git



config.mk is updated to provide this file to boards through the
built-in mechanism:

/include/ ARCH_CPU_DTS

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