arm64: dts: renesas: v3hsk: Add clock-skew for GEther's Micrel PHY

Add the missing clock-skew property for the GEther's Micrel KSZ9031 PHY.

Signed-off-by: Nam Nguyen <nam.nguyen.yh@renesas.com>
Signed-off-by: Phong Hoang <phong.hoang.wz@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/39ab4e92d2242e1d7e83db92f91fc6e0e7e76c47.1675334998.git.geert+renesas@glider.be