arm64: dts: qcom: x1e78100-t14s: Add OLED variant

Since the Lenovo Thinkpad T14s Gen6 is available with an OLED, add
dedicated a dedicated dts for it.

This is needed because the backlight is handled differently for OLED
panels when compared to LCD ones.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20250314140325.4143779-4-abel.vesa@linaro.org


Signed-off-by: Bjorn Andersson <andersson@kernel.org>