drm/tegra: sor: Support device tree crossbar configuration

The crossbar configuration is usually the same across all designs for a
given SoC generation. But sometimes there are designs that require some
other configuration.

Implement support for parsing the crossbar configuration from a device
tree. If the crossbar configuration is not present in the device tree,
fall back to the default crossbar configuration.

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