dt-bindings: panel: Introduce a panel-lvds binding

Following the previous patch, let's introduce a generic panel-lvds
binding that documents the panels that don't have any particular
constraint documented.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220111110635.804371-2-maxime@cerno.tech