zynqmp: pm: Reimplement clock set divider EEMI API

zynqmp: pm: Reimplement clock set divider EEMI API

Clock set divider EEMI API is reimplemented to use system-level clock
set divider EEMI API rather than direct MMIO read/write accesses to clock
control registers.

Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
Acked-by: Will Wong <WILLW@xilinx.com>
Signed-off-by: Jolly Shah <jollys@xilinx.com>