drm/panel: add support for rm69299 visionox panel

Add support for Visionox rm69299 panel.

Signed-off-by: Harigovindan P <harigovi@codeaurora.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
[fix checkpatch warnings, added sentinel ]
Link: https://patchwork.freedesktop.org/patch/msgid/20200421045508.21137-2-harigovi@codeaurora.org