dt-bindings: display: add visionox rm69299 panel variant

Add bindings for visionox rm69299 panel.

Signed-off-by: Harigovindan P <harigovi@codeaurora.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
[fixed indent]
Link: https://patchwork.freedesktop.org/patch/msgid/20200327073636.13823-2-harigovi@codeaurora.org