Merge changes from topic "rd-infra-tftf-support"

* changes:
  feat(rdn2cfg1): add tftf support
  feat(rdn2): add support for tftf
  feat(rdv1): add support for tftf
  feat(plat/sgi): introduce platform variant build option
  refactor(plat/sgi): header files and macros
  fix(build): clean el3 test payload image