feat(scheduled mode): unwind call chain for FFA_MSG_SEND_DIRECT_RESP

This patch performs the action of unwinding the SP call chain upon
FFA_MSG_SEND_DIRECT_RESP invocation.

Change-Id: I26d1ecae2d4c0d21f8780eff0b99f355ea910914
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
diff --git a/src/arch/fake/hypervisor/ffa.c b/src/arch/fake/hypervisor/ffa.c
index 3a9e8dd..2983ef3 100644
--- a/src/arch/fake/hypervisor/ffa.c
+++ b/src/arch/fake/hypervisor/ffa.c
@@ -449,3 +449,11 @@
 	(void)current_locked;
 	(void)receiver_vcpu_locked;
 }
+
+void plat_ffa_unwind_call_chain_ffa_direct_resp(struct vcpu *current,
+						struct vcpu *next)
+{
+	/* Calls chains not supported in the Hypervisor/VMs. */
+	(void)current;
+	(void)next;
+}