test: deny prohibited ABIs while handling CPU_OFF psci msg

FF-A spec states that SPs are prohibited from invoking Direct request,
FFA_RUN and FFA_YIELD interfaces while handling power management
framework message. Make the Cactus SP intentionally invoke prohibited
interfaces and attest that SPMC should deny such invocations.

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: I0a823bf950e3895cb4aff7320c6a0ef7fdec634b
diff --git a/include/runtime_services/ffa_helpers.h b/include/runtime_services/ffa_helpers.h
index 24a7e38..67fd393 100644
--- a/include/runtime_services/ffa_helpers.h
+++ b/include/runtime_services/ffa_helpers.h
@@ -965,6 +965,7 @@
 					    uint32_t status_code);
 
 struct ffa_value ffa_run(uint32_t dest_id, uint32_t vcpu_id);
+struct ffa_value ffa_yield(void);
 struct ffa_value ffa_version(uint32_t input_version);
 struct ffa_value ffa_id_get(void);
 struct ffa_value ffa_spm_id_get(void);