dt-bindings: display: bridge: thc63lvd1024: Document dual-link operation

The THC63LVD1024 LVDS decoder can operate in two modes, single-link or
dual-link. In dual-link mode both input ports are used to carry even-
and odd-numbered pixels separately. Document this in the DT bindings,
along with the related rules governing port and usage.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Tested-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>