Merge changes from topic "ffa_el3_spmc" into integration

* changes:
  feat(spmc): enable checking of execution ctx count
  feat(spmc): enable parsing of UUID from SP Manifest
  feat(spmc): add partition mailbox structs
  feat(plat/arm): allow BL32 specific defines to be used by SPMC_AT_EL3
  feat(plat/fvp): add EL3 SPMC #defines
  test(plat/fvp/lsp): add example logical partition
  feat(spmc/lsp): add logical partition framework