dt-bindings: Add vendor prefix for Ugoos

Ugoos Industrial Co., Ltd. are a manufacturer of ARM based TV Boxes/Dongles,
Digital Signage and Advertisement Solutions [0].

[0] (https://ugoos.com

)

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>