feat(indirect message): send and receive messages

Added helpers to receive and send indirect messages, respectively:
- `receive_indirect_message`;
- `send_indirect_message`;

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I396870f15172f841167627b14c18b1504e0efbee
diff --git a/include/runtime_services/spm_common.h b/include/runtime_services/spm_common.h
index ad2ba08..fb1f61e 100644
--- a/include/runtime_services/spm_common.h
+++ b/include/runtime_services/spm_common.h
@@ -150,4 +150,10 @@
 	ffa_id_t receiver_id,
 	uint32_t mem_func);
 
+bool receive_indirect_message(void *buffer, size_t buffer_size, void *recv,
+			      ffa_id_t *sender, ffa_id_t receiver,
+			      ffa_id_t own_id);
+struct ffa_value send_indirect_message(
+		ffa_id_t from, ffa_id_t to, void *send, const void *payload,
+		size_t payload_size, uint32_t send_flags);
 #endif /* SPM_COMMON_H */