feat(notifications): notifications set and get

Handle FF-A calls FFA_NOTIFICATION_SET and FFA_NOTIFICATION_GET.
The former is used for a sender to signal a notification to the
receiver; the latter is for the receiver to get whichever notifications
there are pending.

Change-Id: I7e9db94201d0d78ceecd599cd350eeb37a8cb1f8
Signed-off-by: J-Alves <joao.alves@arm.com>
diff --git a/src/arch/fake/hypervisor/ffa.c b/src/arch/fake/hypervisor/ffa.c
index c423748..00a0005 100644
--- a/src/arch/fake/hypervisor/ffa.c
+++ b/src/arch/fake/hypervisor/ffa.c
@@ -114,6 +114,24 @@
 	return false;
 }
 
+bool plat_ffa_is_notification_set_valid(struct vcpu *current,
+					ffa_vm_id_t sender_id,
+					ffa_vm_id_t receiver_id)
+{
+	(void)current;
+	(void)sender_id;
+	(void)receiver_id;
+	return false;
+}
+
+bool plat_ffa_is_notification_get_valid(struct vcpu *current,
+					ffa_vm_id_t receiver_id)
+{
+	(void)current;
+	(void)receiver_id;
+	return false;
+}
+
 struct ffa_value plat_ffa_notifications_bitmap_create(
 	ffa_vm_id_t vm_id, ffa_vcpu_count_t vcpu_count)
 {