arm64: zynqmp: Add psu_init_gpl for vck190/vmk180 SC

Add psu_init_gpl file for getting SPL to work directly from the tree.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/6675723ad52d29982e62c6ca4832ed18688076cb.1632488774.git.michal.simek@xilinx.com