Merge changes from topic "ffa_el3_spmc" into integration
* changes:
feat(spmc): add support for direct req/resp
feat(spmc): add support for handling FFA_ERROR ABI
feat(spmc): add support for FFA_MSG_WAIT
feat(spmc): add function to determine the return path from the SPMC
feat(spmd): enable handling of FF-A SMCs with the SPMC at EL3
feat(spmd): update SPMC init flow to use EL3 implementation
feat(spmc): add FF-A secure partition manager core
feat(spmc): prevent read only xlat tables with the EL3 SPMC
feat(spmc): enable building of the SPMC at EL3
refactor(spm_mm): reorganize secure partition manager code