drm/panel: simple: Support for LG lp120up1 panel

The LG lp120up1 TFT LCD panel with eDP interface is a 12.0" 1920x1280
panel, which can be supported by the simple panel driver.

Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>