Merge changes from topic "xlnx_fix_plat_extn_decl_link" into integration

* changes:
  fix(versal2): variable conflicting with external linkage
  fix(versal-net): variable conflicting with external linkage
  fix(versal): variable conflicting with external linkage
  fix(zynqmp): variable conflicting with external linkage
  fix(versal2): add external declaration
  fix(versal): add external declaration
  fix(zynqmp): add external declaration