dt-bindings: Add "vot" vendor prefix

This adds a vendor prefix "vot" for Vision Optical Technology Co., Ltd.
They make LCD displays.

Signed-off-by: David Lechner <david@lechnology.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1513881187-3197-2-git-send-email-david@lechnology.com