Merge changes from topic "xlnx_set_freq" into integration

* changes:
  refactor(xilinx): move plat_get_syscnt_freq2 to common file
  refactor(versal-net): rename VERSAL_NET_IOU_SCNTRS register to generic
  fix(versal-net): setup counter frequency
  fix(versal): initialize cntfrq_el0 register