ARM: dts: exynos: add backlight supply in P4 Note

The LCD backlight  should have a supply.  Use same regulator as LCD, to
silence warning:

  exynos4412-p4note-n8010.dtb: backlight: 'power-supply' is a required property

Link: https://lore.kernel.org/r/20230120155404.323386-8-krzysztof.kozlowski@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>