uboot-imx

arm64: zynqmp: Prepare psu_init rework

Move generic functions to common location psu_spl_init.c. Function
declarations are added to private header.
These changes are done in connection to the fact that still files from
HDF can be copied over and compilation should pass.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>