of: Add United Radiant Technology Corporation vendor prefix

Add vendor prefix for United Radiant Technology Corporation,
a provider of liquid crystal display technologies.

Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>