drm/panel: simple: add Toshiba LT089AC19000

Only exposes a single mode and not a complete display timing, as
the datasheet is rather vague about the minimum/maximum values.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171018172240.8772-1-l.stach@pengutronix.de