drm/panel: simple: add support for NEC NL12880B20-05

This adds support for the NEC LCD Technologies, Ltd. 12.1"
WXGA (1280x800) LVDS TFT LCD panel, which can be supported
by the simple panel driver.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170608180758.31020-1-l.stach@pengutronix.de