Add new argument to hf_mailbox_send.

We don't do anything with it yet, but adding it in a separate patch
reduces the mix of functionality and refactor in the next patch.

Change-Id: I24cbd4d35c4cf9e4985a72d336a68c496c9cc2be
diff --git a/inc/hf/api.h b/inc/hf/api.h
index 1bf9c92..9c86cbf 100644
--- a/inc/hf/api.h
+++ b/inc/hf/api.h
@@ -31,9 +31,8 @@
 				       struct vcpu **next);
 int64_t api_vm_configure(ipaddr_t send, ipaddr_t recv,
 			 const struct vcpu *current);
-
-int64_t api_mailbox_send(uint32_t vm_id, size_t size, struct vcpu *current,
-			 struct vcpu **next);
+int64_t api_mailbox_send(uint32_t vm_id, size_t size, bool notify,
+			 struct vcpu *current, struct vcpu **next);
 struct hf_mailbox_receive_return api_mailbox_receive(bool block,
 						     struct vcpu *current,
 						     struct vcpu **next);