drm/panel: Add support for EDT ETM0430G0DH6

The EDT ETM0430G0DH6 is 4.3" 480x272 panel, which can be
supported by the simple panel driver.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Thierry Reding <treding@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190219140438.17063-2-marex@denx.de