ARM: dts: exynos: move MIPI phy to PMU node in Exynos3250

The MIPI phy is actually part of the Power Management Unit system
controller.  It does not have its own address space, thus keeping the
node under soc causes warnings:

  exynos3250-artik5-eval.dtb: soc: video-phy: {'compatible': ['samsung,s5pv210-mipi-video-phy'],
    '#phy-cells': [[1]], 'syscon': [[15]], 'phandle': [[23]]} should not be valid under {'type': 'object'}

Link: https://lore.kernel.org/r/20230207192851.549242-2-krzysztof.kozlowski@linaro.org


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