dt-bindings: Add Evervision VGG804821 panel

Add device tree bindings for the Evervision VG804821 800x480 5.0" LCD
TFT parallel panel.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190416100645.21689-3-m.felsch@pengutronix.de