soc/tegra: fuse: Register cell lookups for compatibility

Typically nvmem cells would be stored in device tree. However, for
compatibility with device trees that don't contain nvmem cell
definitions, register lookups for cells currently used by consumers.
This allows the consumers to use the same API to query cells from the
device tree or using the legacy mechanism.

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