dt-bindings: display/panel: Add Innolux EJ030NA

Add binding for the Innolux EJ030NA panel, which is a 320x480 3.0" 4:3
24-bit TFT LCD panel with non-square pixels and a delta-RGB 8-bit
interface.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210625121045.81711-1-paul@crapouillou.net