drm/panel: simple: Add support for Kyocera TCG121XGLP panel

The Kyocera TCG121XGLP panel is an XGA LCD TFT panel connected through
LVDS, which can be supported by the simple panel driver.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>