dt-bindings: add vendor TPO

TPO was a merger on June 5 2006 of Toppoly Optoelectronics and
Philips Mobile Display Systems. They manufactured small and medium
mobile displays.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>