arm64: tegra: Add NVIDIA Jetson Nano 2GB Developer Kit support

arm64: tegra: Add NVIDIA Jetson Nano 2GB Developer Kit support

This devkit is very similar to P3450, except it has less RAM, no display
port, and only 3 USB host ports. Derive from P3450 and disable the
hardware that is unavailable.

GPIO PA6 is used to control the HDMI power rail and needs to be on for
hotplug detect to work. This is mapped to the 3.3V USB hub on P3450.
That USB rail is not used here, so delete the regulator to avoid
conflicts.

Signed-off-by: Aaron Kling <webgeek1234@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>