dt-bindings: display: bridge: Convert lvds-transmitter binding to json-schema

Convert the lvds-transmitter binding to DT schema format using
json-schema.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1573660292-10629-2-git-send-email-fabrizio.castro@bp.renesas.com