drm/panel: add support for Foxlink FL500WVR00-A0T panel

This panel is used by Atmel's SAMA5D3 Evaluation Kits (sama5d3xek) and
supported by the simple-panel driver.

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>