Merge changes from topic "ffa_el3_spmc" into integration

* changes:
  feat(fvp): add plat hook for memory transactions
  feat(spmc): enable handling of the NS bit
  feat(spmc): add support for v1.1 FF-A memory data structures
  feat(spmc/mem): prevent duplicated sharing of memory regions
  feat(spmc/mem): support multiple endpoints in memory transactions
  feat(spmc): add support for v1.1 FF-A boot protocol
  feat(plat/fvp): introduce accessor function to obtain datastore
  feat(spmc/mem): add FF-A memory management code