dt-bindings: add vendor prefix for Shenzhen Oranth Technology Co., Ltd.

According to their website (http://www.oranth.com/about-oranth/

)
Shenzhen Oranth Technology Co., Ltd. (or simply "Oranth") "is a
professional Design House & Manufacturer for Android TV Box established
in 2014". One of their brands is Tanix (sometimes also spelled "TANIX").

One of their most popular devices is the "Tanix TX3 Mini" TV box (which
uses the Amlogic S905W chipset).

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>