dt-bindings: display: Convert panel-lvds to DT schema

Convert the panel-lvds binding to use DT schema. The panel-lvds schema
inherits from the panel-common.yaml schema and specific LVDS panel
bindings should inherit from this schema.

Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Maxime Ripard <maxime.ripard@bootlin.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190705164221.4462-10-robh@kernel.org