dt-bindings: Add VXT VL050-8048NT-C01 panel bindings

The VXT VL050-8048NT-C01 is a TFT LCD panel with a 800x480 resolution
connected via 24 width parallel interface.

Reviewed-by: Otavio Salvador <otavio@ossystems.com.br>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190219002706.20077-2-festevam@gmail.com