Merge changes from topic "ffa_el3_spmc" into integration

* changes:
  feat(spmd): allow forwarding of FFA_FRAG_RX/TX calls
  feat(spmc): add support for FFA_SPM_ID_GET
  feat(spmc): add support for forwarding a secure interrupt to the SP
  feat(spmc): add support for FF-A power mgmt. messages in the EL3 SPMC