dt-bindings: display: Add Sony Tulip Truly NT35521 panel support

The Sony Tulip Truly NT35521 is a 5.24" 1280x720 DSI panel, which can
be found on Sony Xperia M4 Aqua phone.  The backlight is managed
through DSI link.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210809051008.6172-2-shawn.guo@linaro.org