Merge changes from topic "qemu_sel2" into integration

* changes:
  docs(build): describes the SPMC_OPTEE build option
  feat(qemu): support el3 spmc
  feat(el3-spmc): make platform logical partition optional
  feat(qemu): support s-el2 spmc
  feat(qemu): update abi between spmd and spmc
  fix(sptool): add dependency to SP image