feat(notifications): information get interface

Handled FFA_NOTIFICATION_INFO_GET interface, to be used by a VM
(receiver's scheduler), Hypervisor or OS kernel.
Returns a list of IDs including Endpoints and vCPUs IDs that have
pending notifications. Provides support for multiple calls to the
FFA_NOTIFICATION_INFO_GET, in case there still are notifications whose
information needs to be retrieved after a call.

Change-Id: I4e73f18ee3301da4829313ffae247b6d0d262622
Signed-off-by: J-Alves <joao.alves@arm.com>
diff --git a/src/arch/aarch64/hypervisor/handler.c b/src/arch/aarch64/hypervisor/handler.c
index 9104028..147c711 100644
--- a/src/arch/aarch64/hypervisor/handler.c
+++ b/src/arch/aarch64/hypervisor/handler.c
@@ -626,6 +626,9 @@
 			ffa_notifications_get_receiver(*args),
 			ffa_notifications_get_vcpu(*args), args->arg2, current);
 		return true;
+	case FFA_NOTIFICATION_INFO_GET_64:
+		*args = api_ffa_notification_info_get(current);
+		return true;
 	}
 
 	return false;