Add support for Hitachi tx18d42vm LVDS LCD panels, these panels have a
lcd controller which needs to be initialized over SPI, once that is
done they work like a regular LVDS panel.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Anatolij Gustschin <agust@denx.de>
Acked-by: Ian Campbell <ijc@hellion.org.uk>