dt-bindings: display: panel: samsung,atna40yk20: document ATNA40YK20

The Samsung ATNA40YK20 panel is a 14" AMOLED eDP panel. It is
similar to the ATNA33XC20 except that it is larger and has a
different resolution.

Signed-off-by: Christopher Obbard <christopher.obbard@linaro.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20250325-wip-obbardc-qcom-t14s-oled-panel-v2-1-e9bc7c9d30cc@linaro.org