ARM: dts: exynos: use Exynos5420 dedicated USB2 PHY compatible

USB2.0 PHY in Exynos5420 differs from Exynos5250 variant a bit, so use the
recently introduced dedicated compatible for Exynos5420.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20201120085637.7299-3-m.szyprowski@samsung.com


Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>