arm64: zynqmp: Use mdio node by vp-x-a2785-00-revA and vpk120-revA

All boards have been converted to use mdio node that's why move ethernet
phys under mdio node too.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/6c60f5d29b9d9992bd0130fd263c8ed13cb8166c.1697115523.git.michal.simek@amd.com