dt-bindings: tegra: Document Jetson Orin Nano

The Jetson Orin Nano is the little sibling of the Jetson Orin NX.
Document the corresponding compatible strings for these devices.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>