drm/panel: simple: Add support for Hitachi TX23D38VM0CAA

The Hitachi TX23D38VM0CAA is a 9" WVGA TFT LCD panel and can be
supported by the simple-panel driver.

This panel is connected via LVDS and uses the data enable signal for
timing. Since HSYNC/VSYNC are ignored, the split between sync length and
porches is arbitrary, as long as the complete horizontal blanking interval
is 256 clocks, and the vertical blanking interval is 45 lines.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>