dt-bindings: Add vendor prefix for DLC Display Co., Ltd.

DLC provides a wide range of display solutions.
Website: http://www.dlcdisplay.com/



Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180523092504.5142-2-m.felsch@pengutronix.de